| Summary: | 博士 === 國立清華大學 === 化學工程學系 === 91 === Experimental and mathematical studies of membrane electrode assembly (MEA) for polymer electrolyte membrane fuel cell (PEMFC) have been conducted. Two MEA fabrication processes derived from the thin-film technique were used to realize the feature as well as to determine possible difficulty in mass production and effects on cell performance. To help us understand the interface between the catalyst layer and the membrane, as well as the membrane expansion when hydration occurs, an isothermal, one-dimensional, steady state model was established to understand the water transport phenomenon in the porous structure of the electrodes and the water content in the membrane. The cathode catalyst layer model was also included to measure the utilization efficiency of the catalyst.
In practice, the swelling of the Nafion film always makes it very difficult to deposit thin catalyst layers on the membrane electrolyte. An innovative process has been developed which utilizes the expansion of Nafion film in the deposition so as to mitigate this problem. When the film is fully expanded, we can apply catalyst ink onto the membrane directly by means of spraying or blade pasting without the concern of swelling. The results of the so-fabricated MEA show good performance relative to commercial product. A decalcomania process for MEA fabrication was also used as the other experiment. Kinetic analysis of the electro-active surface including ac impedance was executed for the two processes.
The simulation of the model with different input parameters, such as the electrode porosity, the stoichiometric coefficient for reactants, the catalyst thickness, and the current density, were correlated with the experimental data.
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