Composite membranes based on micro and mesostructured silica: A comparison of physicochemical and transport properties

The aim of this work is to incorporate inorganic compounds into the Nafion matrix (composite membranes) for high temperature of a polymer electrolyte fuel cell (Tcell > 100 °C). Three silicon oxides having a different morphology were synthesized starting with a tetraethyl orthosilicate as a precursor via sol–gel method: SBA15, SBA15-SH and SiO2. Successively, composite Nafion membranes were prepared using a 3% (w/w) of each powder through a standardized casting method. The influence of SiO2 morphology on chemical–physical properties of the membranes was highlighted resulting in a reduction of the swelling parameters of the composite membranes if compared at T ≥ 80 °C to a recast bare Nafion membrane, used as a reference. Good proton conductivity was also observed for all composite membranes with values of 0.144 S cm−1, 0.136 S cm−1, 0.090 S cm−1and 0.078 S cm−1 recorded at 80 °C (100% RH) for Nrecast, NSBA15, NSBA15-SH and NSiO2, respectively. The polarisation curves carried out at 120 °C (75% RH, 1.5 abs. bar) have revealed a higher stability for NSBA15 membrane after a short time-test, probably because the silica morphology is able to retain water within the polymer matrix and, in accordance to the swelling data.

► The work incorporates inorganic fillers into the Nafion matrix (composite membranes). ► Good proton conductivity was observed for all composite membranes. ► The polarization curves at 120 °C revealed a higher stability for NSBA15 membrane. ► Silica tubular morphology is able to retain water within the polymer matrix. ► It is the first time that this type of fillers is showed in complete fuel-cell tests.