A novel approach for highly proton conductive electrolyte membranes with improved methanol barrier properties: Layer-by-Layer assembly of salt containing polyelectrolytes

The deposition of the self-assembly of PAH/PSS film on Nafion is followed by UV-Vis spectroscopy and it is observed that the polyelectrolyte layers growth on both sides of Nafion membrane regularly. (PAH/PSS)5-Na+ and (PAH/PSS)5-H+ with 1.0 M NaCl exhibits 49.6 and 27.8% reduction in lower methanol permittivity in comparison with the pristine Nafion®117, respectively, while the proton conductivities are 12.97 and 74.69 mS cm−1. Promisingly, it is found that the membrane selectivity values (Φ) of all multilayered membranes in H+ form are much higher than that of salt form (Na+ and Mg2+) and perfluorosulfonated ionomers reported in the literature. Also, we find out that the use of polyelectrolytes with high charge density causes a further improvement in proton conductivity and methanol barrier properties simultaneously. These encouraging results indicate that upon a suitable choice of LbL deposition conditions, composite membranes exhibiting both high proton conductivity and improved methanol barrier properties can be tailored for fuel cells.