A carbon-cloth gas diffusion layer ͑GDL͒ 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. From 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.

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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. From the standpoint 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.

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