Membrane/electrode assembly for polymer electrolyte fuel cells, polymer electrolyte fuel cell, and processes for their production

A process for producing a membrane/electrode assembly for polymer electrolyte fuel cells, comprising a first electrode having a first catalyst layer containing an electrode catalyst and a proton-conductive polymer and a first gas diffusion layer, a second electrode having a second catalyst layer containing an electrode catalyst and a proton-conductive polymer and a second gas diffusion layer, and a polymer electrolyte membrane disposed between the first electrode and the second electrode, wherein the polymer electrolyte membrane has an proton conductivity of at least 0.05 S/cm in an atmosphere at a temperature of 80° C. under a relative humidity of 40%;

• the 90° peel strength between the polymer electrolyte membrane and the first gas diffusion layer is at least 0.03 N/cm;
• and the dimensional change when the first gas diffusion layer is immersed in warm water of 80° C., is less than 10%, which process comprises forming the first catalyst layer on the first gas diffusion layer, and then, bonding the first catalyst layer and the polymer electrolyte membrane.

A process for producing a membrane/electrode assembly for polymer electrolyte fuel cells, comprising a first electrode having a first catalyst layer containing an electrode catalyst and a proton-conductive polymer and a first gas diffusion layer, a second electrode having a second catalyst layer containing an electrode catalyst and a proton-conductive polymer and a second gas diffusion layer, and a polymer electrolyte membrane disposed between the first electrode and the second electrode, wherein the polymer electrolyte membrane has an proton conductivity of at least 0.05 S/cm in an atmosphere at a temperature of 80° C. under a relative humidity of 40%;

• the 90° peel strength between the polymer electrolyte membrane and the first gas diffusion layer is at least 0.03 N/cm;
• and the dimensional change when the first gas diffusion layer is immersed in warm water of 80° C., is less than 10%, which process comprises forming the first catalyst layer on the polymer electrolyte membrane, and then, bonding the first catalyst layer and the first gas diffusion layer.

A polymer electrolyte fuel cell which comprises a membrane/electrode assembly having a polymer electrolyte membrane disposed between an anode having an anode catalyst layer and an anode gas diffusion layer, and a cathode having a cathode catalyst layer and a cathode gas diffusion layer, and a channel to let a gas containing oxygen flow along the surface of the cathode, wherein the 90° peel strength at least one of the interface between the anode and the polymer electrolyte membrane and the interface between the cathode and the polymer electrolyte membrane is at least 0.03N/cm.

A process for producing a polymer electrolyte fuel cell comprising a membrane/electrode assembly having a polymer electrolyte membrane disposed between an anode having an anode catalyst layer and an anode gas diffusion layer, and a cathode having a cathode catalyst layer and a cathode gas diffusion layer, and a channel to let a gas containing oxygen flow along the surface of the cathode, wherein the cathode catalyst layer contains a proton-conductive polymer;

• the proton-conductive polymer contained in the cathode catalyst layer in contact with an inlet of the channel has an ion exchange capacity higher than that of the proton-conductive polymer contained in the cathode catalyst layer in contact with an outlet of the channel;
• and the 90° peel strength at least one of the interface between the anode and the polymer electrolyte membrane and the interface between the cathode and the polymer electrolyte membrane is at least 0.1 N/cm, which process comprises a step of forming the polymer electrolyte membrane, and a step of applying a coating fluid for a catalyst layer containing an electrode catalyst and a proton-conductive polymer to at least one side of the polymer electrolyte membrane to form the anode catalyst layer or the cathode catalyst layer.