Conductivity and Methanol Permeability of Nafion-Zirconium Phosphate Composite Membranes Containing High Aspect Ratio Filler Particles

摘要

Gels of exfoliatedα-zirconium phosphate (ZrP_(exf)) in dimethylformamide (DMF) were used to prepare Nafion/ ZrP_(exf) composite membranes with filler loadings up to 7 wt.-% by casting mixtures of Nafion 1100 solutions in DMF and suitable amounts of 2 wt.-% ZrP gels in DMF. TEM pictures showed that the ZrP_(exf) particles had aspect ratio of at least 20. All samples were characterised by methanol permeability (P) and through-plane (σ_(thp)) and in-plane (σ_(inp)) conductivity measurements at 40℃ and 100% RH. The methanol permeability of Nafion membranes containing in situ grown ZrP particles with low aspect ratio (Nafion/ ZrP_(isg)) was also determined. The methanol permeability and the swelling behaviour of the composite membranes turned out to be strongly dependent on the filler morphology. As a general trend, both permeability and swelling decreased according to the sequence: Nafion/ZrP_(isg) > Nafion > Nafion/ZrP_(exf). The maximum selectivity (σ_(thp)/P = 1.4 × 10~5 S cm~(-3) s) was found for the membrane filled with 1 wt.-% ZrP_(exf): this value is seven times higher than that of Nafion. For the Nafion/ZrP_(exf) membranes, the ratioσ_(inp)/σ_(thp) increases with the filler loading, thus indicating that the preferred orientation of the ZrP sheets is parallel to the membrane surface.