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Study of selected water management strategies for proton exchange membrane fuel cells

University of British Columbia

Proton exchange membrane fuel cells (PEMFC) are a promising energy conversion alternative for a number of applications including automotive, small power generation, and micro applications. However, many issues, such as poor water management and voltage instability, still have to be addressed in order to remove technical barriers to commercialization. In this work, water management issues in PEM fuel cells were investigated in detail with the purpose of developing approaches to reduce the negative effect of liquid water inside the fuel cell. The performance of the PEM fuel cell deteriorates when operated at low humidity to dry conditions. It was demonstrated that the use of perforated sheets as water barrier layers improved the operational life of the fuel cell significantly (>3x) compared to a fuel cell with no additional layers. These sheets increase the water content in the cathode catalyst layer and membrane, via back-diffusion to the anode. In addition, these perforated sheets were also used as a diagnostic tool in order to further investigate the role of cathode and anode MPLs. It was shown that the cathode MPL decreases the water saturation in the catalyst layer and improves water removal via the cathode GDL. It was also shown that the anode MPL plays a role in reducing voltage stability at high flow rates and flooding conditions. Perforated sheets were further explored for use as an engineered gas diffusion layer. This type of approach has the advantage that it can be tailored to specific parameters and conditions. Finally, a new flow field design, used on the cathode side, in which the active area can be modified, is presented and proven to improve the cell voltage and power stability at low power levels. This method increases the effective flow rate inside the flow field by decreasing the active area, resulting in the removal of liquid water and improving the gas diffusion to the cathode catalyst layer. This novel design can also be used to improve cell-to-cell water and gas distribution in fuel cell stacks.

Text

2011-08-11

Attribution-NonCommercial-NoDerivatives 4.0 International

http://hdl.handle.net/2429/36643

Chemical and Biological Engineering

University of British Columbia

UBCV

http://creativecommons.org/licenses/by-nc-nd/4.0/