Effect of Channel Material on Water Droplet Dynamics in a PEMFC Gas Channel

Water accumulation in the gas channels affects the gas diffusion to the reaction sites and the overall performance of proton exchange membrane fuel cells (PEMFCs). Understanding water droplet growth and detachment from the gas diffusion layer (GDL) inside the channel is critical in developing better water management strategies. It has been reported that the wettability of the channel affects the droplet-wall interaction. Hence, in this study, the behavior of the liquid water droplet within a channel is experimentally investigated from a fundamental perspective. Experiments were conducted for different air velocities (0.2-2.4 m/s), GDL types and channel wall materials which are commercially used in PEMFCs for automotive applications. Experimental results were analyzed through the Concus-Finn condition using instantaneous dynamic contact angle (IDCA) to determine the corner filling behavior, which is a precursor to channel flooding. Droplet detachment is influenced by air flow within the channel and the contact angle hysteresis (CAH) of the wall and the GDL material. Experiments were also performed on the GDLs that have undergone longer test periods in a fuel cell. Results showed much lower static CA and CAH, and a corresponding change in the droplet dynamics on used GDL compared to the new GDLs. (C) 2013 The Electrochemical Society. All rights reserved.