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CONTROL OF EFFECTIVE OXYGEN TRANSFER CHARACTERISTICS IN GAS DIFFUSION LAYER WITH MOISTURE FOR PEFC

DOI: 10.1615/ICHMT.2014.IntSympConvHeatMassTransf.440
pages 585-597

Ryo Koresawa
Graduate School of Engineering Yokohama National University, 79-5 Tokiwadai, Hodogaya, Yokohama, Japan

Yoshio Utaka
Yokohama National University, Department of Mechanical Engineering, Tokyo Institute of Technology 2-12-1 0-okayama, Meguro-ku Tokyo 152 JAPAN; School of Mechanical Engineering, Tianjin University, 135 Ya Guan Rd. Tianjin Haihe Education Park, Jinnan District, Tianjin300350, China; Key Laboratory of Efficient Utilization of Low and Medium Grade Energy (Tianjin University), Ministry of Education, China

Аннотация

The mass transfer characteristics of the gas diffusion layer (GDL) in a polymer electrolyte fuel cell are closely related to cell performance. Thus, it is important to clarify the characteristics of water distribution, the microscopic conformation and oxygen diffusivity in a GDL. A hybrid GDL with a wettability distribution is investigated to control the liquid water movement and distribution, as well as to enhance both oxygen diffusion and moisture retention. Hybrid GDLs with different polytetrafluoroethylene (PTFE) contents were prepared to improve the oxygen diffusion characteristics. The effects of different PTFE contents on the effective oxygen diffusivity and water distribution were simultaneously measured using a galvanic cell oxygen absorber and observed via X-ray radiography. The PTFE distribution inside the hybrid GDL was observed using scanning electron microscopy. The formation of oxygen diffusion paths was visualized via X-ray radiography. The pores in the hybrid GDL were first formed in the hydrophobic region and then spread to the untreated region. Thus, the oxygen diffusion characteristics were enhanced by the formation of oxygen diffusion paths in the hydrophobic region. Moreover, the effects of the local PTFE content in the hydrophobic region were elucidated. As a result, a hybrid GDL with approximately 10−20 mass% PTFE in the hydrophobic region was found to have the highest effective oxygen diffusivity.

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