COMPOSITION FOR FORMING CATALYST LAYER, METHOD FOR PRODUCING CATALYST LAYER USING SAME, GAS DIFFUSION ELECTRODE AND ELECTROLYTIC CELL USING SAME

A composition for forming a catalyst layer includes: catalyst particles; a binder; and a solvent, wherein the catalyst particles have an average particle size of primary particles of 1 to 500 nm, the solvent has a surface tension in a range from 23 to 33 mN/m, and the composition has a solid content concentration of 1 to 20 mass %. A gas diffusion electrode incudes: a conductive porous substrate; and a catalyst layer formed on a surface of the conductive porous substrate, wherein the conductive porous substrate has a critical surface tension of less than 29 mN/m, the catalyst layer includes catalyst particles having an average particle size of primary particles of 1 to 500 nm, and a binder, the catalyst layer has a thickness of 10 μm or less, and an area ratio of non-coated portions of the catalyst layer calculated by image analysis is 15% or less.