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: