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Research Papers

# In-Plane Microstructure of Gas Diffusion Layers With Different Properties for PEFC

[+] Author and Article Information
Mehdi Mortazavi

Multiscale Transport Process Laboratory,
Mechanical Engineering-Engineering Mechanics,
Michigan Technological University,
Houghton, MI 49931
e-mail: mortazav@mtu.edu

Kazuya Tajiri

Mechanical Engineering-Engineering Mechanics,
Michigan Technological University,
Houghton, MI 49931
e-mail: ktajiri@mtu.edu

1Address all correspondence to this author.

Contributed by the Advanced Energy Systems Division of ASME for publication in the JOURNAL OF FUEL CELL SCIENCE AND TECHNOLOGY. Manuscript received July 29, 2013; final manuscript received September 27, 2013; published online December 4, 2013. Editor: Nigel M. Sammes.

J. Fuel Cell Sci. Technol 11(2), 021002 (Dec 04, 2013) (9 pages) Paper No: FC-13-1069; doi: 10.1115/1.4025930 History: Received July 29, 2013; Revised September 27, 2013

## Abstract

The gas diffusion layer (GDL) is undoubtedly one of the most complicated components used in a polymer electrolyte fuel cell (PEFC) in terms of liquid and gas transport phenomena. An appropriate fuel cell design seeks a fundamental study of this tortuous porous component. Currently, porosity and gas permeability have been known as some of the key parameters affecting liquid and gas transport through the GDL. Although these are dominant parameters defining mass transport through porous layers, there are still many other factors affecting the transport phenomena and overall cell performance. In this work, the microstructural properties of Toray carbon papers with different thicknesses and for polytetrafluoroethylene (PTFE) treated and untreated cases have been studied based on scanning electron microscopy (SEM) image analysis. The water droplet contact angle, as a dominant macroscale property, along with the mean pore diameter, pore diameter distribution, and pore roundness distribution, as important microscale properties, have been studied. It was observed that the mean pore diameter of Toray carbon paper does not change with its thickness and PTFE content. Mean pore diameter for Toray carbon papers was calculated to be around $26μm$, regardless of their thicknesses and PTFE content. It was also observed that the droplet contact angle on the GDL surface does not vary with the GDL thickness. The average contact angle for the 10 wt. % PTFE treated GDLs of different thicknesses was measured at about $150 deg$. Finally, the heterogeneous in-plane PTFE distribution on the GDL surface was observed to have no effect on the mean pore diameter of GDLs.

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## Figures

Fig. 1

SEM image processing steps

Fig. 2

Droplet contact angle on treated and untreated GDLs

Fig. 3

GDL mean pore size as a function of its thickness

Fig. 4

SEM image of different locations on a treated GDL sample

Fig. 5

Pore diameter distribution for GDLs of different thicknesses

Fig. 6

Pore diameter distribution for three random locations on untreated TGP-120

Fig. 7

Pore roundness distribution of GDLs

Fig. 8

The variation of the calculated mean pore diameter as a function of the threshold for TGP-060

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