(578f) Graphene Oxide Modification of Poly(styrene-isobutylene-styrene) (SIBS) As Proton Exchange Membranes for Fuel Cell Applications

In recent years graphene and its derivatives have gained increasing attention due to their low cost, good mechanical stability, excellent conductivity, and the variety of properties that can be obtained with them. Among these materials graphene oxide (GO) shows good hydrophilicity and proton transport, due to its high surface area and its surface chemistry, which makes it suitable for proton exchange membrane fuel cell (PEMFC) applications. GO has been incorporated into a sulfonated poly(styrene-isobutylene-styrene) (SIBS) matrix in order to enhance its water retention and proton conductivity, while blocking the transport of methanol through the membrane. Upon the incorporation of GO a significant change in morphology has been observed in SAXS patterns. This change in morphology influences the properties of the polymeric membrane. In addition, no significant chemical shifts have been observed using FT-IR after incorporation of the GO, suggesting there are poor specific chemical interactions between the GO and the ionic domains in the polymer. However, changes in the intensity of some bands have been observed, suggesting interference of the additives with the vibrations of the bonds. As expected water absorption was enhanced, even with low loadings of the filler. Nonetheless, the effects on methanol permeability and ion exchange capacity were different with each loading and were not related to the amount of water absorbed. Proton conductivity at low temperatures was reduced but the enhancement on proton conductivity is more significant at high temperatures, as suggested in the literature. These results suggest that the polymer nanocomposite membrane composed of GO in SIBS matrix has tremendous potential for direct methanol fuel cell applications (DMFC).  Further studies such as the incorporation of functionalized GO, and the incorporation of different loadings of the GO with different chemical functionalizations have been encouraged.