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Insight into the Structure and Nanoscale Conductivity of Fluorinated Ionomer Membranes

Hiesgen, Renate and Morawietz, Tobias and Handl, Michael and Corasaniti, Martina and Friedrich, K. Andreas (2014) Insight into the Structure and Nanoscale Conductivity of Fluorinated Ionomer Membranes. Journal of The Electrochemical Society, 161 (12), F1214-F1223. Electrochemical Society, Inc.. DOI: [10.1149/2.0701412jes] ISSN 0013-4651

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A material-sensitive atomic force microscopic (AFM) tapping mode was combined with current measurements to investigate structure, phase separation, and conductive structure of surfaces and cross sections of long side chain Nafion and short side chain AQUIVION PFSA ionomer membranes. We found unexpected large-scale ordered structures consistent with a dominant lamellar polymer structure at the cross sections. The highly terraced areas of both ionomers have a wide distribution of layer thicknesses from sub-nanometer to a few nanometers. In both broad size distributions, preferential sizes were identified that reflect the different lengths of the molecular side chains, indicating a stacking in layers. The nanoscale phase separation of the ionomer was analyzed by using the capacitive current distribution. In AQUIVION PFSA, larger connected water-rich ionic areas were found than in Nafion with same total ionic area. A steady-state current at the cross sections evolved only after an activation period by enforcing current flow though the membrane. A comprehensive and heterogeneous current distribution was observed with highly conductive areas. In contrast, on outer membrane surfaces, only non-continuous spot-like currents were observed. In general, our measurements are consistent with conduction in water layers in-between polymer chains and a bi-continuous structure under faradaic current flow.

Item URL in elib:https://elib.dlr.de/91881/
Document Type:Article
Title:Insight into the Structure and Nanoscale Conductivity of Fluorinated Ionomer Membranes
AuthorsInstitution or Email of AuthorsAuthors ORCID iD
Hiesgen, RenateHochschule EsslingenUNSPECIFIED
Morawietz, TobiasHochschule EsslingenUNSPECIFIED
Handl, MichaelHochschule EsslingenUNSPECIFIED
Corasaniti, MartinaHochschule EsslingenUNSPECIFIED
Friedrich, K. Andreasandreas.friedrich (at) dlr.deUNSPECIFIED
Date:August 2014
Journal or Publication Title:Journal of The Electrochemical Society
Refereed publication:Yes
Open Access:Yes
Gold Open Access:No
In ISI Web of Science:Yes
DOI :[10.1149/2.0701412jes]
Page Range:F1214-F1223
Publisher:Electrochemical Society, Inc.
Keywords:Polymer membranes, nanoscale conductivity, fuel cells
HGF - Research field:Energy
HGF - Program:Efficient Energy Conversion and Use (old)
HGF - Program Themes:Fuel Cells (old)
DLR - Research area:Energy
DLR - Program:E EV - Energy process technology
DLR - Research theme (Project):E - Electrochemical Processes (old)
Location: Stuttgart
Institutes and Institutions:Institute of Engineering Thermodynamics > Electrochemical Energy Technology
Deposited By: Friedrich, Prof.Dr. Kaspar Andreas
Deposited On:17 Nov 2014 16:20
Last Modified:31 Jul 2019 19:49

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