Characterization of surface ionic activity of proton conductive membranes by conductive atomic force microscopy

The conductivity of a proton-conducting membrane (PEM) depends on the characteristics of the ionic clusters both within the polymeric structure and on its outer surfaces. This work explores the use of conductive atomic force microcopy to characterize the surface ionic activity of these membranes and investigates the effect of the surface ionic activity on the performance of PEM fuel cells. Results obtained show that only a fraction of the membrane surfaces is active and that this fraction increases with the relative humidity in the gas phase. Also, no correlation exists between the membrane surface ionic activity and its topography as expected. (c) 2005 The Electrochemical Society.