CATALYST INK FOR FORMING ELECTRODE CATALYST LAYER AND METHOD OF PRODUCING MEMBRANE ELECTRODE ASSEMBLY

A catalyst ink which can be directly applied to a polymer electrolyte membrane without producing wrinkles or cracks in the catalyst layer and without lowering performance, and a membrane electrode assembly using the catalyst ink. The catalyst ink for an electrode catalyst layer includes a solvent. The solvent contains catalyst-supported carbon particles which are carbon particles supporting a catalyst, a polymer electrolyte, and at least one of carbon fibers and organic electrolyte fibers. The solvent has a particle size distribution which a first peak lies in a range of 0.1 μm or more and 1 μm or less, and a second peak lies in a range of 1 μm or more and 10 μm or less. The catalyst ink is directly applied to a polymer electrolyte membrane to produce a membrane electrode assembly.