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 °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 °C for NRecast, NSBA-16 and NSiO2 respectively. Polarisation curves carried out at 100 °C have revealed a better performance for composite membranes (NSBA-16) than NRecast with a similar trend of proton conductivity.

► Two silica with different morphology are introduced into the matrix of Nafion.
► The silica increased the water retention of the membranes at high temperature.
► Operating temperature of the membrane was increased (T > 100 °C).
► Membranes with SBA-16 have been investigated for the first time in PEM fuel cell.
► NSBA-16 membrane offers higher maximum power density 445 mW cm−2 at 100 °C.