Thesis Abstracts 2005
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Development of Experimental Methods for Studying Gas Diffusion Layer Effects in Direct Methanol Fuel Cells
By: Memphis K. Don, MSc
Abstract
The possibility of using methanol liquid fuel directly in the fuel cell makes DMFCs a very promising electrochemical power source. Significant research has been conducted on the cell's key technical challenges such as slow anode kinetics and methanol crossover, but without great emphasis on the Gas Diffusion Layer (GDL) properties.
Several experimental methods for physical and performance characterization of commercially available GDLs are investigated with the aim of correlating physical properties with cell performance. To segregate cathode GDL effects, DMFC performance was observed with methanol /air, hydrogen/air, and methanol/ nitrogen.
Preliminary results indicate that mechanical factors such as MEA compression seem to have a much larger impact on cell performance then other physical characteristics like GDL thickness, pTFE loading or micro-porosity. Although little performance change was observed in H2/Air operated cells, felt based GDLs underperformed by approximately 25% in the DMFC cathode. This diminished performance could be attributed to these GDL's poor resistivity characteristics as compared to paper based products, and sluggish water removal from the cathode due to the presence of a meso-porous region. Through these methods the amount of methanol crossover could be measured. As well, it was observed that CO 2 crossed over directly from the DMFC anode.
Overall, consistent characterization methods have been developed in our laboratory that can accurately observe GDL effects on the DMFC cathode performance, which could be employed in future investigations.
