CATALYST LAYER, CATALYST LAYER FORMING LIQUID AND MEMBRANE ELECTRODE ASSEMBLY

To provide a catalyst layer, a catalyst layer forming liquid, and a membrane electrode assembly, capable of forming a fuel cell excellent in power generation efficiency.The catalyst layer of the present invention comprises a supported catalyst having a carrier containing a metal oxide and a catalyst supported on the carrier; and a polymer having at least one type of units containing a cyclic ether structure, selected from the group consisting of units (u11), units (u12), units (u21) and units (u22), and having an ion exchange group, wherein the total of the content of the units containing a cyclic ether structure is at least 30 mol% to all units which the polymer contains: