Evaluation of smectite clays as nanofillers for the synthesis of nanocomposite polymer electrolytes for fuel cell applications

Synthetic and natural smectite clays, with different structural and physical parameters,were tested as nanofillers for the creation of Nafion nanocomposites. The solution intercalationmethod has been successfully applied for incorporation of layered materials intothe polymer, while the effect of the solvent, temperature and filler loading were examinedin order to determine the optimum conditions for the preparation of highly homogeneouscomposites.NMR methods, including pulsed-field-gradient spin-echo (PFGSE) and spin-latticerelaxation time (T1) were used to investigate behavior of water confined in recast Nafionand in Nafioneclay hybrids membranes.The transport mechanism appears to be influenced from the dimensions of thedispersed platelets and mainly from the type of nanocomposites formed upon mixing theclay particles with the polymer matrix. Compared to pure Nafion, the water uptake and thewater diffusion of the hybrid membranes are increased, with the exception of the Kunipia-Nafion composite. A remarkable behaviour at high temperature is observed, wherecomposite membranes maintain stable and unwavering diffusion for many hours and inconditions of not humidification, proving the exceptional water retention property of thesematerials. Finally the hybrid membranes are much stiffer and can withstand highertemperatures compared to pure Nafion, hence both these characteristics are highlydesirable for use in fuel cell applications.