Abstract
Nafion®/functionalied silica composite membranes have been prepared using 3-aminopropyl-trimethoxysilane (NH2-silane)、Trimethoxy(propyl)silane (R-silane)、(3-Mercaptopropyl)trimethoxy-silane (SH-silane) via hydrolysis sol-gel reaction then followed by solution casting. Nafion®/sulfonated silica composite membranes were prepared using Nafion®/silica-SH composite membranes oxidiated by 10 wt% H2O2 solution. The results indicated that the optimum oxidiation condition was at 60℃ within 1 hr. Physical and chemical properties of the composite membranes were characterized by FT-IR, XPS, 29Si-NMR, DSC and SEM. The performance of the Nafion®/functional silica composite membranes was evaluated in terms of methanol permeability, proton conductivity and cell performance. The Nafion®/0.6 wt% silica–SO3H composite membranes possess a higher conductivity (0.1338 S/cm) than that of pristine Nafion® (0.1256 S/cm). The Nafion®/0.6 wt% silica–NH2 composite membranes showed a lower methanol permeability (3.99*10-6 cm2/s) than that of pristine Nafion® (5.51*10-6 cm2/s). The current densities were measured as 70、72.5 and 62.5 mA cm-2 at a potential of 0.2 V for Nafion®/0.6 wt% silica–SO3H、Nafion®/0.6 wt% silica–NH2 and pristine Nafion®, respectively. The maximum power density was 15.18、16.05 and 13.04 mW cm2, respectively. Composite membranes containing 0.6 wt% silica–SO3H or 0.6 wt% silica–NH2 possess high proton conductivity and low methanol permeability will be suitable for DMFC application.