| Summary: | 碩士 === 國立成功大學 === 航空太空工程學系碩博士班 === 98 === The proton exchange membrane fuel cells (PEMFC) is one of the most promising alternatives of the new energy. Due to difficulties of the hydrogen transportation and storage, it becomes a tendency to use reformers to supply the hydrogen-rich reformate for the fuel cell system in recent years. However, there are some problems if the reformate is used as the fuel of RMFCs. In addition to the drawback of the low hydrogen concentration, the reformate contains many other kinds of gases which may cause negative effects on the PEMFC performance.
In this study, the author focuses on the effects of carbon monoxide (CO) which is one of the most critical impurities. The effects of the CO concentration and hydrogen concentration on the PEMFC behavior were investigated while the mixed gases composed by hydrogen, nitrogen and CO were introduced to the anode of an MEA where the Pt-Ru catalyst was coated.
In the experiments of the hydrogen-nitrogen mixed gas, it was observed that the concentration polarization appeared in conditions of the insufficient hydrogen flow rate and it might result in a drop of the PEMFC performance. However, the effect of hydrogen concentration on the power output was not significant. When CO was further introduced to the diluted hydrogen, it caused a significant decrease of the PEMFC performance. CO resulted in not only a decrease of voltage, but also an acceleration of voltage drop.
When the CO concentration was increased, it caused significant drop of the fuel cell performance, in spite of nitrogen to be introduced in the mixed hydrogen or not. It was also observed that the increase of the CO concentration resulted in an increase of the voltage drop. Furthermore, when the CO concentration was higher than 100 ppm, the cell voltage fluctuated, and it therefore resulted in an unsteady output of the performance. This phenomenon can be interpreted by the interaction of the oxidation rate of CO and the adsorption rate of CO on the catalyst which are functions of the anodic overpotential.
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