Method to Resolve Transport Distance for Oxygen Diffusion in the Land-Channel Geometry of a PEMFC

Abstract

Land-channel geometry is known to cause significant current density distribution in the land-channel direction of a PEMFC. Previously, many modeling studies and a few experimental studies have shown significant variation of current density in the land-channel direction such as [1-2]. There are two prime sources of such variation: (1) non-uniform transport distance for gas diffusion from channel to the catalyst layer, and (2) non-uniform transport distance for product water generated at catalyst layer to the channel. Baker et. al. defined a shape factor f (> 1)  that removes anisotropy originated from land-channel geometry and gas diffusion layer (GDL) properties to provide resultant thickness of fh where h is thickness of a GDL [3].

We present a method to evaluate local transport distance in the land-channel geometry of a PEMFC. A segmented cell is developed to measure current density and high frequency resistance distribution in land-channel direction at sub-millimeter resolution of 350 μm. In this study, 1 mm wide land and channel configuration and GDL without microporous layer is used. Limiting current analysis reported in literature [4] is utilized to measure local limiting current at given resolution and then transport resistances were estimated.

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2. U.N. Shrivastava, K. Tajiri. J. of Electrochem. Soc., 162, F722 (2015).
3. D. R. Baker, D. A. Caulk, K. C. Neyerlin, and M. W. Murphy. J. of Electrochem. Soc., 156, B991 (2009).
4. J. St-Pierre, B. Wetton, G.-S. Kim, and K. Promislow, J. of Electrochem. Soc., 154, B186 (2007).