Sulfonated Silica-Poly(dimethylsiloxane) Hybrid Membranes for Proton Exchage Membrane Fuel Cells

Abstract

Free-standing, flexible and thermally stable membrane, a hybrid of sulfonated silica and poly (dimethylsiloxane) (PDMS) was synthesized for proton exchange membrane fuel cells (PEMFCs) and its properties were analyzed. PDMS was reacted with 3-mercaptopropyl trimethoxysilane (MPTMS) by sol-gel process with acid catalyst. Thiol group (-SH) in MPTMS was oxidized into sulfonic group (-SO3H) during the reaction, which enabled the membrane proton conductible. Reaction conditions and weight ratio of PDMS and MPTMS decided the brittleness of membrane. Ca. 20wt% of MPTMS and more than 48hr of aging time were essential for acquiring free-standing and crackles membrane. Sequence of adding precursors was also crucial to membrane’s properties.As a result, synthesized membrane showed ca. 7.84% of water uptake ability and ca. 0.0424S/cm of proton conductivity (at 60℃, 100% RH.) at most.