Multiple layer membranes for fuel cells employing direct feed fuels

摘要

A cation exchange membrane having a laminated structure of at least three layers of cation exchange polymer. In a membrane in accordance with the invention, the cation exchange polymer in the laminate has a polymer backbone and cation exchange groups carried on recurring side chains attached to the polymer backbone with the number of carbon atoms in the polymer backbone in relation to the cation exchange groups defining an ion exchange ratio (IXR) for each layer. The layers have differing IXR values which provide one or more high IXR layers and one or more low IXR layers with the IXR of the low IXR layers being less than about 17 and the IXR of the high IXR layers being at least about 15. In a membrane in accordance with the invention, the high and low layers further provide a change in IXR of at least about 2 in at least two locations across the thickness of the membrane.