Membrane electrode assembly for polymer-electrolyte fuel cell and method for its manufacture

摘要

A membrane electrode unit contains a polymer electrolyte membrane with porous reaction layers on both sides. The reaction layers have a inhomogeneous microstructure made of a proportion of catalyst A1 impregnated with ionomer and embedded in the ionomer and a residual proportion of catalyst A2. Ratio of A1:A2 is 1-20:1, preferably 3-10:1. Independent claims are also included for: (I) the production of a membrane electrode unit comprising (1) preparing an ink A by dispersing a proportion of catalyst A1 in a solution of ionomer in a solvent A; (2) preparing an ink B by dispersing a proportion of a catalyst A2 in a solvent B; (3) purifying ink A and ink B to form a common ink C; (4) homogenizing ink C; (5) coating a polymer electrode unit with ink C; and (6) drying the coating; and (II) the ink used in the above production containing catalyst, ionomer and organic solvent. Solvent A and B are miscible with each other and solvent B does not dissolve the ionomer.