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

摘要

[PROBLEMS] This invention provides a membrane electrode assembly comprising an electrode catalyst layer which can enhance water retention without inhibiting, for example, the diffusivity of a reaction gas and the removal of water produced by an electrode reaction and can exhibit a high level of power generation performance under low humidification conditions, and a process for producing the membrane electrode assembly. [MEANS FOR SOLVING PROBLEMS] A membrane electrode assembly comprises a polymer electrolyte membrane held between a pair of electrode catalyst layers and is characterized in that the electrode catalyst layer comprises particles bearing thereon a polymer electrolyte and a catalyst material, and, in the electrode catalyst layer, the volume of pores with a diameter of 1.0 µm or less in terms of cylinder approximation of the pores as calculated by mercury porosimetry increases from the electrode catalyst layer surface located on the outer side to the polymer electrolyte membrane located on the inner side.