Spatially Resolved Contact Pressure and Contact Resistance Measurements at the Gas Diffusion Layer: A Tool for PEM Fuel Cell Development

A device and a method for direct measurement of the local contact pressures of gas diffusion layers (GDL) are presented. The new tool determines the spatially resolved contact pressure on the GDL side opposite to the flow-field/GDL interface which is relevant to good electrical contact between the GDL and the catalyst coated membrane (CCM) in a practical fuel cell setting. In a second step, using a fit function determined by separate two and four point resistance measurements, the method is extended to deliver spatially resolved contact resistance data. These experimental methods, in addition to shear-force measurements, are applied to a range of state-of-the-art GDL media. Whereas the shear-force measurements correlate well with data from recent work in the literature, the comparison of a non-woven and a paper based GDL with distinct differences in their shear moduli shows almost the same contact pressures underneath the flow field channel. This result indicates that shear-force data alone is of limited use for predicting contact pressure underneath flow field channels. In-situ current/voltage curves confirm the predictive power of a direct measurement of the contact pressure which highlights the importance for future GDL development and modeling activities. (C) 2012 The Electrochemical Society. [DOI: 10.1149/2.054206jes] All rights reserved.