Proton conductivity and methanol permeation in Nafion™/ORMOSIL prepared with various organic silanes

Abstract

Using TEOS and organic silane agent, we could prepare the Nafion™/ORMOSIL hybrid membranes with varying hydrophilicity and morphology by controlling the number and the type of organic groups. Water uptake was dominated by the hydrophilicity of hybrid membranes. On the other hand, methanol uptake was determined by the interconnectivity and the compatibility of ORMOSIL phase. It is due to the difference of polarity between water and methanol. Methanol permeability was directly correlated with the uptakes of both water and methanol which reflect how many paths for the methanol diffusion were formed. The methanol sorption was directly related to methanol uptake. In addition, the higher the methanol diffusion, the higher the wet porosity of membranes in methanol–water solvent. The type of organic groups as well as the hydrophilicity and the distribution of ORMOSIL phase could affect proton conductivity. Nafion™/[ORMOSIL (TEOS:TEVS=1:1)] had much lower proton conductivity while Nafion™/[ORMOSIL (TEOS:DEDMS=0:1)] had much higher proton conductivity.