Evaluation of PEFC Membrane based on Cross-linked PTFE by EB Grafting: Effect of Thickness for FC Performance

Abstract

The performance of a polymer electrolyte fuel cell (PEFC) was affected by the thickness of the thin proton exchange membrane (PEM). The PEMs with the different thickness were prepared by radiation induced grafting of styrene into the radiation-cross-linked polytetrafluoroethylene (RX-PTFE) membrane prepared from PTFE dispersion, and then sulfonated. The wet thicknesses of the obtained thin PEMs were lower than 25 μm. A PEM based on a 50 μm PTFE film, with the wet thickness of 73 μm, was also prepared under the same procedure for the comparison. The obtained PEMs were characterized in term of gas cross-over. The surface of platinum / carbon electrodes was coated with Nafion ® dispersion, and then membrane electrode assembles (MEAs) were prepared by the hot-pressing. The polarization curves and electrochemical impedances of the thin PEMs in a single fuel cell were analyzed. As a result, the cell performance of the MEA based on thinner PEM tended to give higher power density and current density. On the other hand, the performance of the thinnest PEM (13 m) decreased, and the MEA based on the thinner PEM gave the lower open circuit voltage (OCV) due to the higher gas cross-over. Thus, the thin PEM based on RX-PTFE had shown a high performance at the suitable thickness.