Characterization of sulfated-zirconia/Nafion® composite membranes for proton exchange membrane fuel cells

An interesting new material based on a Nafion® membrane doped with a sulfated-zirconia filler is presented. This filler is unique in that the filler itself can contribute to the proton conductivity due to the presence of acidic functionalities on the surface of the filler. The presence of the filler in the membrane results in the deprotonation of Nafion®’s acid moieties as indicated by the absence of the acid mode at 1475 cm−1 in the FTIR spectrum. Spectra from DSC, DMA and broadband electric spectroscopy (BES) show the presence of several molecular transitions, two of which are detected in the BES permittivity profiles. The membrane exhibits a reasonably high conductivity (3 × 10−3 S cm−1 at 120 °C) even in completely dry conditions, which makes it a promising material for an anhydrous fuel cell. The conductivity behaviour exhibits a mix of Arrhenius and VTF behaviours and is closely tied to the dielectric relaxations.

► Interesting new material based on Nafion® doped with sulfated-zirconia filler.
► Membrane exhibits a conductivity of 3 × 10−3 S cm−1 at 120 °C in dry conditions.
► Presence of filler results in the deprotonation of Nafion®’s acid moieties.
► Correlation between molecular relaxations and electric polarizations.
► Effect of water on the conduction mechanism and the molecular relaxations.