A performance evaluation of direct methanol fuel cell using impregnated tetraethyl-orthosilicate in cross-linked polymer membrane

A sulfonated styrene-(ethylene-butylene)-sulfonated styrene (SEBSS) is a highly sulfonated random block polymer. This material has several characteristics including high proton conductivity, good mechanical properties, and relatively low cost, but the chemical and temperature stability is lower than that of perfluorinated polymers such as Nafion® due to lower C–H bond association enthalpies of the hydrocarbon framework in polymer. In this paper, we developed the chemical and temperature stability of sulfonated styrene polymer membrane by impregnating silica in these polymers in order to overcome the humidification constraints in direct methanol fuel cell (DMFC). We modified a composite membrane by including a small amount of silica with the aim of retaining the electrochemically produced water inside the cell. A composite sulfonated SEBSS membrane was synthesized by the blending of inorganic materials such as tetraethylorthosilicate. Membrane cast from this material was investigated in relation to methanol permeability in the range of methanol concentration from 2 to 4 M at 30°C. SEM Photograph revealed a brittle, surface-attached silica layer with silicon oxide contents. The thermal decomposition of a composite membrane was investigated by TG-DSC thermograms. The I–V characteristics of DMFC using a composite membrane as electrolyte was studied with a single cell test equipment at the temperature of 30–90°C. The highest current densities are 74, 229, and 442 mA / cm 2 at temperatures 30, 60, and 90°C at a potential of 0.3 V , when small amounts of silica of 0.014 mol was added to SEBSS polymer.