Proton exchange membranes, such as the widely used Nafion membranes, are essential components in industrial proton-exchange membrane fuel cells. In this study, multilayer sulfonated carbon-nanotubes/Nafion composite membranes with high performances have been prepared using layer-by-layer assembly. The membranes consist of a certain number of equally thick sulfonated carbon-nanotubes/Nafion layers. The thickness of the layers varies from 40 μm to 0.5 μm. This study indicates that the multilayered structure in composite membranes, especially in membranes with ultrathin layers (<1 μm)...
