Conductivity and Methanol Permeability of Nafion–Zirconium Phosphate Composite Membranes Containing High Aspect Ratio Filler Particles
✍ Scribed by M. Casciola; G. Bagnasco; A. Donnadio; L. Micoli; M. Pica; M. Sganappa; M. Turco
- Publisher
- John Wiley and Sons
- Year
- 2009
- Tongue
- English
- Weight
- 283 KB
- Volume
- 9
- Category
- Article
- ISSN
- 1615-6846
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✦ Synopsis
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.