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Fig. 1 Chemical structure of tested membranes: Flemion®S and Nafion®117 Gas permeability

Hydrogen and oxygen permeability were estimated by a measurement system in which wet gases were flowed on the both sides of the membrane in order to keep the membrane uniformly wet as shown in Fig. 2. Membranes were set in the ribbed cell made of PTFE after drying at 100°C for 1 hour. Humidified test gas was flowed on one side of the meihbrane set in the cell and humidified inert gas was flowed on the other side. This inert gas was same as the carrier gas used in the gas chromatograph. The driving force for the permeation of the test gas (using an inert gas as the carrier) through the membrane was the partial pressure difference between one side of the membrane and the another. Concentration of the test gas in the inert gas was measured by gas chromatograph. Nitrogen and helium were used as carrier gas of the gas chromatograph for the measurement of hydrogen and oxygen, respectively. Temperature of the cell and the humidifiers were changed in the range from 30°C to 85°C during the measurements. This method was used not only for the evaluation of gas permeation behavior of plain membranes but also for that of membrane-electrode composites.

Ion Exchange Membrane

Ion Exchange Membrane

Gas Sampler Gas Chromatograph Integrator

Fig. 2 Flow diagram of gas permeability measurement system

Gas Sampler Gas Chromatograph Integrator

Fig. 2 Flow diagram of gas permeability measurement system

Preparation of membrane-electrode composites ,

Membrane-electrode composites (assemblies) were prepared by several methods such as hotpressing and "adhesion method" in which adhesives developed by AGC are used and the assembling is carried out by pressing slightly at room temperature. The latter method can afford smaller decrease in pore volume of gas diffusion electrode than the former one as shown in Fig.3. The adhesives contain fluorocarbon compounds and can be noninflammable.

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