Development of direct methanol fuel cell using a novel electrolyte membrane for automobiles

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Direct methanol solid polymer fuel cell (DMFC).is expected as a power source for automobiles, because fuel itself is liquid and response against load fluctuation win be fast, and weight of system will be light. However, following problems have also been addressed. Methanol transport through the electrolyte membrane and oxidized without make electrical energy. The operation temperature is too low for the catalytic reaction because of electrolyte thermal durability. When a polyelectrolyte membrane which shows high proton conductance, barrier property against methanol and high temperature durability till 200℃, is developed, DMFC system will be applied for electric automobile power source. In this study, a new polyelectrolyte membrane for DMFC was developed, and the membrane performances were evaluated as a new fuel cell system as a power for electric automobile. Using plasma-graft polymerization method, the new pore filling type solid electrolyte was prepared. The pore filling electrolyte … More polymer was covalently bonded to the pore surface of the substrate, and the substrate matrix maintains the structure of the membrane under high temperature, and the substrata matrix suppress the filling polymer swelling against the feed. The swelling suppression leads to barrier property against methanol transport. The polymer morphology and properties were maintained till the temperature that it thermally decomposed. Acrylic acid and sodium vinylsulfonate were polymerized in the porous polytetrafluoroethylene substrate of which the heat-resistance is high, and an electrolyte film was synthesized. The grafted polymer was formed in the substrate pores, and the grafted polymer formation profile can be controlled by changing plasma treatment and grafting conditions.To introduce sulfonate group in the electrolyte grafted polymer, the electric charge repulsion must be decreased. Salt was added in the monomer solution, and the salt effectively decrease the repulsion effect, and polyelectrolyte with relatively high sulfonate group density can be obtained with the salt addition. Prepared membrane showed relatively high proton conductance. Finally, the pore filling polyelectrolyte showed the methanol transport resistance at high temperature around 200℃. Less