CATALYST LAYER, CATALYST LAYER INK AND MEMBRANE-ELECTRODE ASSEMBLY

The present invention provides a catalyst layer, a catalyst layer ink and a membrane-electrode assembly which enable provision of fuel cells with high power efficiency. The catalyst layer of the present invention comprises a carbon alloy catalyst and an ion exchange polymer which comprises at least one species of units having a cyclic ether structure selected from the group consisting of units represented by the formula (u11), units represented by the formula (u12), units represented by the formula (u21), units represented by the formula (u22) and units represented by the formula (u24).