Analysis of gas diffusion layer and flow-field design in a PEMFC using neutron radiography

A carbon-cloth gas diffusion layer (GDL) displays better performance than a carbon-paper GDL under humidified conditions. A straight flow field displays better performance than a serpentine flow field. To investigate these phenomena, neutron radiography was used to compare the amount of liquid water that accumulated in test fuel cells. It was found that a larger amount of water accumulated in a carbon-cloth GDL than in a carbon-paper GDL. Front the viewpoint of cell performance, the carbon-cloth GDL was less influenced by the accumulated water than the carbon-paper GDL. It is assumed that the broader pore distribution of a carbon-cloth GDL creates oxygen-diffusion paths even if water accumulates in the GDL. With a serpentine flow field, water accumulated in the corner and the gas bypassed the flow field. These phenomena are the main causes of performance deterioration with a serpentine flow field. (C) 2008 The Electrochemical Society.