Probing liquid water saturation in diffusion media of polymer electrolyte fuel cells

Neutron radiography (NR) was intended to visualize the accumulation and distribution of product water inside diffusion media (DM) in a polymer-electrolyte fuel cell (PEFC). However, the two-dimensional NR technique is unable to separate anode water from cathode water and resolve the liquid water distribution along the cell thickness, two pieces of information strongly needed to characterize the level of cathode DM flooding or anode dry-out. In this paper, NR data analysis is performed for the first time in the context of a three-dimensional two-phase PEFC model. The numerical study illustrates the difficulty in NR data analysis where the major concern originates from the separation of liquid water in the cathode DM from the water in thick membranes, or from liquid water in the anode DM for the thin membrane case. In addition, the two-phase simulation results show that the calculated amount of water according to NR conditions is well within the range measured by NR experiments in the literature, demonstrating the validity of the present two-phase model. A concern is raised whether the two-dimensional NR technique is suitable for studying water management, which generally requires separation of water between the anode and cathode. (c) 2006 The Electrochemical Society. All rights reserved.