(P. Prapainainar).2 Highlight  Silane treated mordenite composite membrane was used for DEFC.  Four types of silane coupling agents were treated on MOR surface.  Sulfhydryl group in MPTES provided sulfonic group for enhance proton conductivity.  MOR-MPTES/Nafion membrane had the highest selectivity at all temperature. AbstractMordenite (MOR) has been used to solve the alcohol crossover in direct ethanol fuel cells. However, the lack of compatibility has been a problem. This paper shows the compatibility improvement of MOR in a Nafion composite membrane for use in a fuel cell using four types of silane coupling agents: gamma-glycidoxypropyltrimethoxysilane (GMPTS), (3-mercaptopropyl) trimethoxysilane (MPTS), (3-Mercaptopropyl) triethoxysilane (MPTES) and (3-Mercaptopropyl) methyl-dimethoxysilane (MPDMS). The coupling agents were used to treat the MOR surface before mixing with Nafion. Each type of silane was treated carefully and differently, depending on its structure. Their characterizations were also described. The results showed that better compatibility and a noticeable reduction in ethanol permeability were achieved when using all silane-treated MOR in the composite. It was found that the Nafion/MOR-MPTES membrane had the highest proton conductivity at all temperature ranges from 30-70 o C. This was due to the fact that the sulfhydryl (-SH) functional group in MPTES provided the sulfonic group in its structure after the oxidation in the surface treatment process. These sulfonic groups at the MOR surface facilitated proton transport and improved the selectivity of the membrane.

Composite membranes, consist of Nafion and surface-modified mordenite as inorganic filler functioned as ethanol barrier, were prepared and used for direct ethanol fuel cell (DEFC). mordenite was modified using gamma-glycidoxypropyltrimethoxysilane (GMPTS) which has the epoxide group and 3-mercaptopropyl-trimethoxysilane (MPTS) which has the mercapto group as coupling agents on mordenite. The composite membranes were fabricated by adding 5 %weight modified mordenite into Nafion by solution casting and hot pressing with catalyst to produce MEA and tested in DEFC single cell stack. XRD, FT-IR, Mastersizer and SEM were used to study the morphology, physical and chemical properties of the filler and the composite membrane. The characterizations also included ethanol permeability and proton conductivity by using the diffusion cell and AC impedance test, respectively. The performance of the cell was evaluated in the DEFC under cell temperature from 30 to 70 °C and ethanol concentration of 1 M to 4 M. It was then compared to the recasted Nafion membrane.