Liquid-Water Uptake and Removal in PEM Fuel-Cell Components [electronic resource]

• Ngôn ngữ: eng
• Ký hiệu phân loại: 621.3 Electrical, magnetic, optical, communications, computer engineering; electronics, lighting
• Thông tin xuất bản: Berkeley, Calif. : Oak Ridge, Tenn. : Lawrence Berkeley National Laboratory ; Distributed by the Office of Scientific and Technical Information, U.S. Dept. of Energy, 2011
• Mô tả vật lý: Size: 9 : , digital, PDF file.
• Bộ sưu tập: Metadata
• ID: 256865
• Chủ đề: 1. 30 direct energy conversion; 2. Water, fuel cell, catalyst layer, gas diffusion layer, capillary pressure, droplet

Tóm tắt

Management of liquid water is critical for optimal fuel-cell operation, especially at low temperatures. It is therefore important to understand the wetting properties and water holdup of the various fuel-cell layers. While the gas-diffusion layer is relatively hydrophobic and exhibits a strong intermediate wettability, the catalyst layer is predominantly hydrophilic. In addition, the water content of the ionomer in the catalyst layer is lower than that of the bulk membrane, and is affected by platinum surfaces. Liquid-water removal occurs through droplets on the surface of the gas-diffusion layer. In order to predict droplet instability and detachment, a force balance is used. While the pressure or drag force on the droplet can be derived, the adhesion or surface-tension force requires measurement using a sliding-angle approach. It is shown that droplets produced by forcing water through the gas-diffusion layer rather than placing them on top of it show much stronger adhesion forces owing to the contact to the subsurface water.