A modified Nafion membrane with extremely low methanol permeability via surface coating of sulfonated organic silica.

We developed a method to significantly decrease the methanol permeability of a Nafion membrane that does not require sacrificing its proton conductivity and mechanical stability. The Nafion membrane modified by the coating of a thin layer of sulfonated organic silica on the membrane surface exhibits significantly decreased methanol permeability--the permeability is decreased to an undetectable level--while retaining an acceptable ionic conductivity of 0.029 S cm(-1).