Influence of silica morphology in composite Nafion membranes properties

The introduction of inorganic compounds into the Nafion polymeric matrix represents a possible solution to increase the operative temperature (T > 100 degrees C) without losing the conductivity, water transport properties and above all improving the mechanical characteristics. Two silica materials with different morphologies were synthesized via sol-gel method (SiO2 and SBA-16) by a tetraethyl orthosilicate (TEOS, 98%, Aldrich). Composite Nafion membranes were prepared using a 3%wt/wt of each powder and a standardized casting method. The influence of morphology on chemical-physical properties of membranes was investigated. It was highlighted that the silica introduction reduces the swelling parameters compared to bare Nafion membrane (NRecast) at room temperature. A similar behaviour was observed also in the proton conductivity measurements, in fact values of 0.144 S/cm, 0.114 S/cm and 0.078 S/cm were recorded at 80 degrees C for NRecast, NSBA-16 and NSiO2 respectively. Polarisation curves carried out at 100 degrees C have revealed a better performance for composite membranes (NSBA-16) than NRecast with a similar trend of proton conductivity. Copyright (C) 2011, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.