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Nanoscale properties of polymer fuel cell materials - A selected review

Hiesgen, Renate and Wehl, Ines and Aleksandrova, Elena and Roduner, Emil and Bauder, Alexander and Friedrich, K. Andreas (2010) Nanoscale properties of polymer fuel cell materials - A selected review. International Journal of Energy Research, 34, pp. 1223-1238. Wiley. DOI: 10.1002/er.1661

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Abstract

The properties of the components of a membrane electrode assembly in a polymer electrolyte fuel cell (PEFC) determine its efficiency and performance. This paper aims at demonstrating the importance of nanoscale properties of PEFC membranes and electrodes and discussing the information obtained by various experimental techniques. The nanostructure and conductivity of freshly prepared as well as artificially degraded Nafion membranes and Pt/C electrodes are investigated by contact atomic force microscopy (AFM), conductive AFM, pulsed force mode (PFM)-AFM, in situ scanning tunnelling microscopy (STM), and scanning electron microscopy. The different techniques can provide complementary information on structure and conductivity. With in situ STM on Pt catalyst covered graphite, a layer of very small Pt particles between the catalyst particles is imaged, which is probably not visible with TEM and can explain a systematic discrepancy between TEM and XRD in particle size distribution. Conductive AFM is used to investigate the conductivity of Nafion. The images show a quite inhomogeneous distribution of current at the surface. The percentage of conductive surface increases with humidity, but regions without any current still present up to 80% of relative humidity (RH). Comparison with PFM-AFM images, where differences in adhesion forces are measured, indicates that hydrophobic regions are present at the surface with comparable dimensions, which are attributed to non-conductive PTFE-like polymer backbone. The changes in hydrophilic and hydrophobic parts after artificial degradation by plasma etching in air plasma can be imaged by PFM. High-resolution current images of the membrane were used to directly compare the measured nanostructure of the single conductive channels with model predictions from the literature. Recent models in the literature propose the formation of water-filled inverted micelles, with a mean diameter of 2.4 nm, and their agglomeration into clusters agrees well with the current images

Item URL in elib:https://elib.dlr.de/66708/
Document Type:Article
Title:Nanoscale properties of polymer fuel cell materials - A selected review
Authors:
AuthorsInstitution or Email of AuthorsAuthors ORCID iD
Hiesgen, Renaterenate.hiesgen (at) hs-esslingen.deUNSPECIFIED
Wehl, Inesines.wehl (at) hs-esslingen.deUNSPECIFIED
Aleksandrova, Elenaelena.aleksandrova (at) uni-stuttgart.deUNSPECIFIED
Roduner, Emilemil.roduner (at) uni-stuttgart.deUNSPECIFIED
Bauder, Alexanderalexander.bauder (at) dlr.deUNSPECIFIED
Friedrich, K. Andreasandreas.friedrich (at) dlr.deUNSPECIFIED
Date:October 2010
Journal or Publication Title:International Journal of Energy Research
Refereed publication:Yes
Open Access:No
Gold Open Access:No
In SCOPUS:Yes
In ISI Web of Science:Yes
Volume:34
DOI :10.1002/er.1661
Page Range:pp. 1223-1238
Publisher:Wiley
Status:Published
Keywords:Niedertemperatur Brennstoffzellen; polymer membran, degradation
HGF - Research field:Energy
HGF - Program:Efficient Energy Conversion (old)
HGF - Program Themes:E EV - Energy process technology (old)
DLR - Research area:Energy
DLR - Program:E EV - Energy process technology
DLR - Research theme (Project):E - Elektrochemische Prozesse (old)
Location: Stuttgart
Institutes and Institutions:Institute of Engineering Thermodynamics > Electrochemical Energy Technology
Deposited By: Friedrich, Prof.Dr. Kaspar Andreas
Deposited On:30 Nov 2010 14:56
Last Modified:08 Mar 2018 18:38

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