| Summary: | 碩士 === 國立中央大學 === 能源工程研究所 === 102 === This study used a commercial high temperature proton exchange membrane (PEM) electrode assembly Advent TPS®, with a conventional graphite serpentine flow channel and recently developed metal foam flow channel, to assemble a PEM fuel cell. Effects of operating temperature, stoichiometry, gas preheating temperature, humidification on cell performance are investigated. AC impedance analysis is also used to study the changes in various resistances inside the cell, and verify corresponding electrochemical mechanism.
Results show that metal foam flow channel having high gas permeability improves gas convection and diffusion, and increase the chance of reaction with the platinum catalyst. The porous structure of metal foam can effectively reduce the contact resistance between the flow plate and carbon paper. The current density at 0.6 V is approximately 40 % higher than conventional graphite serpentine flow channel, when using oxygen as the oxidant. Increasing the operating temperature, stoichiometry, or humidification, improved the cell performance. The equivalent circuit model of AC impedance used in the analysis can describe the electrochemical mechanism of fuel cell.
In long time operation test, we observe the performance began to decline after 200 hours, and is mainly related to the decay of catalyst.
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