A composite electrolyte membrane containing high-content sulfonated carbon spheres for proton exchange membrane fuel cells

Sulfonated carbon spheres (SCS) were employed with perfluorinated ionomers as a binder to make proton-conducting electrolyte membranes for polymer electrolyte membrane fuel cells (PEMFC). Hot-pressing produced a symmetric, thin membrane with SCS particles concentrated in the center of the membrane. Relative to Nafion, the SCS materials showed higher density of sulfonic acid groups and increased water retention capacity of the membrane. This is the favorable condition for effective back diffusion of water from cathode preventing dehydration of membrane. As a result, the SCS membrane showed much better performance in single cell PEMFC operation than Nafion membrane. The membrane also showed much improved tolerance to chemical degradation by oxygen radical species.