CHEMICAL AND MORPHOLOGICAL CHARACTERIZATION OF A DIRECT METHANOL FUEL-CELL BASED ON A QUATERNARY PT-RU-SN-W C ANODE/

Conventional and 'paste process' methods were investigated to fabricat e the membrane/electrode assembly (M&E) for application in a vapour-fe ed direct methanol fuel cell. A quaternary Pt-Ru-Sn-W/C and a Pt/C cat alysts were employed for methanol oxidation and oxygen reduction, resp ectively. The structure and chemical composition of the catalysts were investigated by transmission electron microscopy (TEM) and X-ray powd er diffraction (XRD). A crystalline Pt f.c.c. phase was found to preva il in both catalysts. Agglomeration and twinned particles were frequen tly observed in the Pt-Ru-Sn-W/C catalyst.(-) Electrochemical investig ations were performed by a.c.-impedance spectroscopy and galvanostatic polarization. The 'paste process' based assembly showed a significant ly lower uncompensated resistance and an approximately two-fold power density increase with respect to the conventional assembly. According to the scanning electron microscopy analysis the observed results were attributed to improved bonding between catalysts and perfluorosulfoni c membrane and to a larger extension of the three-phase reaction zone in the 'paste process' based assembly.