Accumulation and Removal of Liquid Water in Proton Exchange Membrane Fuel Cells

Removal of liquid water from proton exchange membrane fuel cells is critical for efficient performance, low temperature operation, and robustness for start-up under freezing conditions. The present work investigates the three-dimensional location of liquid water during steady-state operation and the governing mechanisms that control its accumulation and removal. A combination of ex situ and in situ methods with neutron imaging diagnostics is used to investigate water transport in the bulk materials and flow field channels. These results provide experimental evidence of the mechanisms by which water vapor condenses in the anode during operation and the transport resistance for its removal during shutdown purge. Based on these results, a one-dimensional model is proposed that can be applied to calculate the effectiveness of cathode purge starting from a wide range of fuel cell shutdown conditions. (C) 2009 The Electrochemical Society. [DOI: 10.1149/1.3242295] All rights reserved.