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

Abstract

Abstract Gels of exfoliated α‐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 °C 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 ratio σ inp /σ thp increases with the filler loading, thus indicating that the preferred orientation of the ZrP sheets is parallel to the membrane surface.