Meso-structured organosilicas as fillers for Nafion® membranes

The processing and characterization of composite membranes casted from commercial Nafion® suspension with incorporation of benzene-bridged periodic mesoporous organo-silicas functionalised with sulfonic acid groups (S-Ph-PMO) are presented in the search for improved protonic conductivity under low humidity conditions. It is shown that the incorporation of 10 wt.% S-Ph-PMO fillers into Nafion® improves the proton conductivity by approximately 70%, with the composite membranes reaching 0.19 S · cm^{- 1} in 98% relative humidity (RH), or 0.05 S · cm^{- 1} in 60% RH, at 94 °C. The filler effect on the conductivity increases at low RH, representing an enhancement of ~ 250% and ~ 425% with respect to the conductivity of Nafion® at 40% RH and 20% RH, respectively. The conductivity improvement is also higher at low temperature due to the higher activation energy of Nafion®. Such effects are interpreted by the high proton mobility in the stable mesoporous channels of the fillers.