Theoretical examination of effective oxygen diffusion coefficient and electrical conductivity of polymer electrolyte fuel cell porous components

• Published in: Journal of power sources Vol. 327; pp. 610 - 621
• Main Authors: Inoue, Gen, Yokoyama, Kouji, Ooyama, Junpei, Terao, Takeshi, Tokunaga, Tomomi, Kubo, Norio, Kawase, Motoaki
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 30.09.2016
• Subjects: Electrical conductivity; FIB-SEM; Gas diffusion coefficient; PEFC; Porous electrode; X-ray CT; FIB-SEM; X-ray CT; Gas diffusion coefficient; Electrical conductivity; Porous electrode; PEFC
• ISSN: 0378-7753; 1873-2755
• DOI: 10.1016/j.jpowsour.2016.07.107

The reduction of oxygen transfer resistance through porous components consisting of a gas diffusion layer (GDL), microporous layer (MPL), and catalyst layer (CL) is very important to reduce the cost and improve the performance of a PEFC system. This study involves a systematic examination of the relationship between the oxygen transfer resistance of the actual porous components and their three-dimensional structure by direct measurement with FIB-SEM and X-ray CT. Numerical simulations were carried out to model the properties of oxygen transport. Moreover, based on the model structure and theoretical equations, an approach to the design of new structures is proposed. In the case of the GDL, the binder was found to obstruct gas diffusion with a negative effect on performance. The relative diffusion coefficient of the MPL is almost equal to that of the model structure of particle packing. However, that of CL is an order of magnitude less than those of the other two components. Furthermore, an equation expressing the relative diffusion coefficient of each component can be obtained with the function of porosity. The electrical conductivity of MPL, which is lower than that of the carbon black packing, is considered to depend on the contact resistance. •Actual porous electrode structures of PEFC were made with FIB-SEM and X-ray CT.•Both gas diffusion results of calculations and experiments were almost same.•Equations of relative diffusion coefficient of each porous media were obtained.•Catalyst layer had low gas diffusion property depending on ionomer as expected.