Electrolyte membrane, membrane electrode assembly using this and fuel cell

An electrolyte membrane having ionic conductivity, the electrolyte membrane comprising:

• a base material, and
• organic molecules containing ion exchange groups;
• wherein the organic molecules are chemically bonded to a surface of the base material to form an organic layer,
• wherein ions are conducted via the ion exchange groups in the organic layer,
• the base material is a porous membrane, wherein a plurality of through holes that pierce the porous membrane in a direction perpendicular to a surface of the porous membrane are formed in the porous membrane,
• the organic molecules are chemically, bonded to an inner surface of the through holes and form the organic layer, and
• in the through holes, a water repellent substance is further provided on a face of the organic layer on a side opposite to a face that is bonded to the base material, and the water-repellent substance fills gaps present in an inner portion of the through holes,
• wherein the water-repellent substance is a polymer of a precursor material of the water-repellent substance polymerized in capillaries that remain in an inner portion of the through hole, and a smallest cross-sectional area of each of the through holes is in a range of 3 nm2 to 300 nm2.