Direct measurement of through-plane thermal conductivity and contact resistance in fuel cell materials

An experimental study to determine the through-plane thermal conductivity of dry Nafion (R), various diffusion media, catalyst layer, and the thermal contact resistance between diffusion media and a metal plate as a function of temperature and pressure was performed. Dry Nafion((R)) thermal conductivity was determined to be 0.16 +/- 0.03 W m(-1) K-1 at room temperature, which decreases to 0.13 +/- 0.02 W m(-1) K-1 at 65 degrees C. Diffusion media thermal conductivity was found to be function of PTFE content and manufacturer, and was 0.48 +/- 0.09 W m(-1) K-1 for untreated and 0.22 +/- 0.04 W m(-1) K-1 for 20 wt.% PTFE treated SIGRACET((R)) diffusion media, respectively. Toray diffusion media thermal conductivity was measured to be 1.80 +/- 0.27 W m(-1) K-1 at 26 degrees C and decreases to 1.24 +/- 0.19 W m(-1) K at 73 degrees C. The thermal contact resistance between Toray carbon paper and aluminium bronze material was determined to vary from 6.7 x 10(-4) to 2.0 x 10(-4) m(2) K W-1 for an increase in compression pressure from 0.4 to 2.2 MPa. The equivalent thermal conductivity of a 0.5 mg cm(-2) platinum loaded catalyst layer was estimated to be 0.27 +/- 0.05 W m(-1) K-1. A one-dimensional analytical model was also used to estimate the temperature drop in the fuel cell components. A maximum of 3-4 degrees C temperature drop can be expected for a 200 mu m thick SIGRACET((R)) diffusion media at 1 A cm(-2). The thermal properties characterized should be useful to help modelers accurately predict the temperature distribution in a fuel cell. (c) 2006 Elsevier B.V. All rights reserved.