Effect of Bulk and Surface Treatments on the Surface Ionic Activity of Nafion Membranes

Abstract

The ionic activity at the interfaces of the membrane and the ionic polymer phase in the catalyst layers can have a significant impact on the transport rates of protons and water in a proton exchange membrane fuel cell (PEMFC). This study investigated the effects of some treatment processes on the surface ionic activity of extruded membranes and their performance in a PEMFC. The treatment processes included and wash and plasma sputter and reactive ion etching. The membrane surface ionic activity was determined by the ratio using X-ray photoelectron spectroscopy. The results showed that the surface of these membranes, as received and after wash, had lower ionic activity than that of its bulk ( vs 0.053). Treatment with had a significant impact on the surface ionic activity, lowering the surface ratio further to 0.017. The -rich skin of extruded Nafion membranes could be removed by sputter etching with argon exposing a surface with higher ionic activity . However, reactive ion etching with and argon led to a further decrease in the surface ionic activity . Fuel cell results showed a strong correlation between the membrane surface ionic activity and the fuel cell performance.