Characterization of Interfacial Structure in PEFCs: Water Storage and Contact Resistance Model

In this work, an analytical model of the microporous layer (MPL) and the catalyst layer (CL) interface under compression is developed to investigate the effects of the MPL|CL interfacial morphology on the ohmic and mass transport losses at the MPL|CL interface in a polymer electrolyte fuel cell (PEFC). The model utilizes experimentally measured surface profile data as input. Results indicate that the uncompressed surface morphology of mating materials, the elasticity of PEFC components, and the local compression pressure are the key parameters that influence the characteristics of the MPL and CL contact. The model predicts that a 50% drop in the MPL and CL surface roughness may result in nearly a 40% drop in the MPL|CL contact resistance. The model also shows that the void space along the MPL|CL interface can potentially store a significant amount of liquid water (0.9-3.1 mg/cm(2)), which could result in performance loss and reduced durability. A 50% drop in the MPL and CL surface roughness is expected to yield nearly a 50% drop in the water storage capacity of the MPL|CL interface. The results of this work provide key insights that will enhance our understanding regarding the complex relation between MPL|CL interfacial structure and cell performance. (C) 2009 The Electrochemical Society. [DOI:10.1149/1.3247585] All rights reserved.