Ion transport mechanism in hybrid MF-4SC membranes modified by silica and posphotungstic heteropoly acid

Transport properties of MF-4SC perfluorinated cation-exchange membrane composites containing hydrous silica and phosphotungstic heteropoly acid (PTA) nanoparticles were studied at various temperatures. Modification of an MF-4SC membrane increases its ion conductivity under reduced humidity by 2.5 orders of magnitude compared to the unmodified membrane and makes the material less humidity-dependent. Comparison of NMR and impedance spectroscopy data implies that water molecules are involved in ion transport in the test samples. Most likely that modification changes the membrane structure at the nanoscale (broadens channels and increases pores) and generates an additional net of hydrogen bonds involving a dopant and sulfo groups of the membrane.