| Summary: | 碩士 === 國立臺灣科技大學 === 材料科技研究所 === 93 === The aim of this study was to develop new proton exchange membranes for low temperature DMFC for the substitution of the Nafion membrane showing high cost and poor barrier to methanol crossover. Because of its good chemical stability, film-fabrication ability and low cost, PVA was chosen to be the matrix of developed membranes. There were two systems developed in this study. One is a modified PVA membrane cross-linked and sulfonized with glutaraldehyde and chlorosulfonic acid, respectively. The other is an organic-inorganic hybrid PVA membrane in which PVA sulfonated with chlorosulfonic acid is organic matrix and then inorganic matrix was formed from the reaction between Tetraethoxysilane (TEOS) and Trimethyl phosphate (TMP). Various analysis techniques were used to characterize the structure and study the physical and thermal properties, proton conductivity as well as methanol permeability of the developed membranes. The CSPVA-30-1h membrane showed the best proton conductivity of 2.8910-3 S/cm among the modified PVA membranes at 30 oC in flooded state. The methanol permeability of the CSPVA-45-3h membrane was measured to be 3.2610-7 cm2/s about one order less than that of the Nafion membrane. It was found that a significant reduction in methanol crossover could be achieved using the modified PVA membrane. Among the organic-inorganic hybrid membranes, SPVA/SiO2/P2O5, the best proton conductivity was obtained to be 5.310-3 S/cm for the SPSP-612-1h membrane at 30 oC in flooded state. In addition, higher proton conductivity of ~1.010-2 S/cm could be achieved at 75 oC and 80% R.H.
The relationship between the characteristics and the proton conductivity as well as the methanol permeability for the developed membranes is also discussed in this study.
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