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Updated: May 29, 2026

Ion-Exchange Membranes for the Fabrication of Reverse Electrodialysis Device
Published on: July 20, 2021
Correlating humidity-dependent ionically conductive surface area with transport phenomena in proton-exchange
Qinggang He1, Ahmet Kusoglu, Ivan T Lucas
1Environmental Energy Technologies Division, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, California 94720, United States.
Abstract:
The objective of this effort was to correlate the local surface ionic conductance of a Nafion 212 proton-exchange membrane with its bulk and interfacial transport properties as a function of water content. Both macroscopic and microscopic proton conductivities were investigated at different relative humidity levels, using direct-current voltammetry and current-sensing atomic force microscopy (CSAFM). We were able to identify small ion-conducting domains that grew with humidity at the surface of the membrane. Numerical analysis of the surface ionic conductance images recorded at various relative humidity levels helped determine the fractional area of ion-conducting active sites. A simple square-root relationship between the fractional conducting area and observed interfacial mass-transport resistance was established. Furthermore, the relationship between the bulk ionic conductivity and surface ionic conductance pattern of the Nafion membrane was examined.
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