MEMBRANE ELECTRODE ASSEMBLY, PROCESS FOR PRODUCING MEMBRANE ELECTRODE ASSEMBLY, SOLID POLYMER FUEL CELL

摘要

[PROBLEMS] To provide a membrane electrode assembly comprising an electrode catalyst layer which can enhance water retention without inhibiting, for example, the diffusibility of reaction gas and the removal of water produced in an electrode reaction, and can exhibit a high level of power generation properties even under low humidified conditions, and a process for producing the membrane electrode assembly. [MEANS FOR SOLVING PROBLEMS] A membrane electrode assembly comprising a polymer electrolyte membrane held between a pair of electrode catalyst layers, characterized in that the electrode catalyst layer comprises particles supporting thereon a polymer electrolyte and a catalyst material and, in the electrode catalyst layer, the proportion of the polymer electrolyte defined by {mass of polymer electrolyte)/(mass of particles in the particles supporting the catalyst material)} reduces from the surface of the electrode catalyst layer on the outer side toward the polymer electrolyte membrane on the inner side.