Thailand: Degussa — fumed silica

Abstract

Durability of an organic–inorganic nanocomposite electrolyte membrane prepared by mixing hydrophilic fumed silica particles of an average size of 7 nm with Nafion ionomer was studied for the mitigation of chemical degradation of the membrane caused by trace radial species in polymer electrolyte fuel cells (PEFCs). Infrared (IR) spectroscopy indicated that the peak of C−F, S−O and C−O−C bands were not shifted to the higher wavenumber with an addition of 1 wt.% hydrophilic silica to the Nafion matrix. This suggests that hydrophilic silica had a catalyst activity for the decomposition of hydrogen peroxide and reduced the membrane degradation by trace radicals attack. Quantum chemical calculations (QCCs) using a model ionomer of trifluoromethanesulfonate (TFMS) and a model nanoparticle of Si(OH)4 also implied that the nanoparticle was able to trap H, OH and OOH radical species before attacking the ionomer. The hydration of TFMS that induces deprotonation of sulfonic acid group in TMFS and formation of hydronium anion was confirmed also in the presence of trace radicals due to the ability of Si(OH)4 to trap H radical.