An electrolyte membrane is described that has improved bondability with a catalyst layer and that achieves good power generation performance, without the electrolyte membrane undergoing a physical treatment and without any loss of surface modification effect, where the electrolyte membrane comprises a polymer electrolyte and a nonionic fluorochemical surfactant.

A composite polymer electrolyte membrane including a polymer electrolyte and a porous substrate, and having a dry tensile modulus of 100 N/cm or more per width and a wet tensile modulus of 35 N/cm or more per width. Enhancing the mechanical characteristics of the electrolyte membrane results in providing an electrolyte membrane that achieves good dry-wet cycle durability.

A membrane electrode assembly for the fuel cell includes a solid polymer electrolyte membrane, an anode catalyst layer assembled to one surface of the solid polymer electrolyte membrane, and a cathode catalyst layer assembled to another surface of the solid polymer electrolyte membrane. The membrane electrode assembly contains cerium ions. The membrane electrode assembly includes a power-generation region and a non-power-generation region. The power-generation region includes the catalyst layers on both surfaces of the solid polymer electrolyte membrane in a center portion. The non-power-generation region is without the catalyst layer on at least one surface of the solid polymer electrolyte membrane in an outer periphery portion. A cerium ion content per area in the power-generation region is larger than a cerium ion content per area in the non-power-generation region.

A membrane electrode assembly for the fuel cell includes a solid polymer electrolyte membrane, an anode catalyst layer assembled to one surface of the solid polymer electrolyte membrane, and a cathode catalyst layer assembled to another surface of the solid polymer electrolyte membrane. The membrane electrode assembly contains cerium ions. The membrane electrode assembly includes a power-generation region and a non-power-generation region. The power-generation region includes the catalyst layers on both surfaces of the solid polymer electrolyte membrane in a center portion. The non-power-generation region is without the catalyst layer on at least one surface of the solid polymer electrolyte membrane in an outer periphery portion. A cerium ion content per area in the power-generation region is larger than a cerium ion content per area in the non-power-generation region.

The present invention relates to a membrane electrode unit comprising a polymer membrane doped with a mineral acid as well as two electrodes, characterized in that the polymer membrane comprises at least one polymer with at least one nitrogen atom and at least one electrode comprises a catalyst which is formed from at least one precious metal and at least one metal less precious according to the electrochemical series.

The present invention relates to a membrane electrode unit comprising a polymer membrane doped with a mineral acid as well as two electrodes, characterized in that the polymer membrane comprises at least one polymer with at least one nitrogen atom and at least one electrode comprises a catalyst which is formed from at least one precious metal and at least one metal less precious according to the electrochemical series.

An electrolyte membrane of a membrane-electrode assembly is formed by a manufacturing method yielding a membrane with improved chemical durability. The manufacturing method includes preparing an antioxidant solution, mixing the antioxidant solution and a first ionomer dispersion solution, drying the mixture to produce a composite having an antioxidant and a first ionomer surrounding the antioxidant, introducing and mixing the composite with a second ionomer dispersion solution, and applying that mixture to a substrate and drying the mixture to manufacture an electrolyte membrane. The resulting electrolyte membrane includes the composite having an antioxidant in an ionic state and a first ionomer surrounding the antioxidant.

An electrolyte membrane of a membrane-electrode assembly is formed by a manufacturing method yielding a membrane with improved chemical durability. The manufacturing method includes preparing an antioxidant solution, mixing the antioxidant solution and a first ionomer dispersion solution, drying the mixture to produce a composite having an antioxidant and a first ionomer surrounding the antioxidant, introducing and mixing the composite with a second ionomer dispersion solution, and applying that mixture to a substrate and drying the mixture to manufacture an electrolyte membrane. The resulting electrolyte membrane includes the composite having an antioxidant in an ionic state and a first ionomer surrounding the antioxidant.

An electrode catalyst layer includes a catalyst material, a conductive carrier that supports the catalyst material, a polymer electrolyte containing a sulfonate group, and a fibrous material. The electrode catalyst layer includes a first surface configured to be in contact with the polymer electrolyte membrane, and a second surface facing away from the first surface. A first value is obtained by dividing a peak intensity of SO.sub.3 (m/z80) by a peak intensity of carbon (m/z12), and also dividing by a total thickness of the electrode catalyst layer, when the electrode catalyst layer is analyzed using time-of-flight secondary ion mass spectrometry (TOF-SIMS) at each of a plurality of positions in a thickness direction of the electrode catalyst layer from the first surface to the second surface. A rate of change of the first value with respect to a thickness of the electrode catalyst layer is −0.0020 or less.

An electrode catalyst layer includes a catalyst material, a conductive carrier that supports the catalyst material, a polymer electrolyte containing a sulfonate group, and a fibrous material. The electrode catalyst layer includes a first surface configured to be in contact with the polymer electrolyte membrane, and a second surface facing away from the first surface. A first value is obtained by dividing a peak intensity of SO.sub.3 (m/z80) by a peak intensity of carbon (m/z12), and also dividing by a total thickness of the electrode catalyst layer, when the electrode catalyst layer is analyzed using time-of-flight secondary ion mass spectrometry (TOF-SIMS) at each of a plurality of positions in a thickness direction of the electrode catalyst layer from the first surface to the second surface. A rate of change of the first value with respect to a thickness of the electrode catalyst layer is −0.0020 or less.