Effect of interface on surface morphology and proton conduction of polymer electrolyte thin films

To understand the relationship between surface morphology and proton conduction of polymer electrolyte thin films, perfluorinated ionomer Nafion® thin films were prepared on different substrates such as glassy carbon (GC), hydrophilic-GC (H-GC), and platinum (Pt) as models for the ionomer film withi...

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Bibliographic Details
Published in:Physical chemistry chemical physics : PCCP 2013-07, Vol.15 (27), p.11494-11500
Main Authors: OHIRA, Akihiro, KURODA, Seiichi, MOHAMED, Hamdy F. M, TAVERNIER, Bruno
Format: Article
Language:English
Subjects:
Carbon - chemistry
Chemistry
Electrochemical Techniques
Electrolytes
Electrolytes - chemistry
Exact sciences and technology
Film thickness
Fluorocarbon Polymers - chemical synthesis
Fluorocarbon Polymers - chemistry
General and physical chemistry
Ionomers
Microscopy, Atomic Force
Morphology
Particle Size
Platinum
Platinum - chemistry
Polymeric films
Proton conduction
Protons
Surface physical chemistry
Surface Properties
Thin films
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Summary:To understand the relationship between surface morphology and proton conduction of polymer electrolyte thin films, perfluorinated ionomer Nafion® thin films were prepared on different substrates such as glassy carbon (GC), hydrophilic-GC (H-GC), and platinum (Pt) as models for the ionomer film within a catalyst layer. Atomic force microscopy coupled with an electrochemical (e-AFM) technique revealed that proton conduction decreased with film thickness; an abrupt decrease in proton conductance was observed when the film thickness was less than ca. 10 nm on GC substrates in addition to a significant change in surface morphology. Furthermore, thin films prepared on H-GC substrates with UV-ozone treatment exhibited higher proton conduction than those on untreated GC substrates. However, Pt substrates exhibited proton conduction comparable to that of GCs for films thicker than 20 nm; a decrease in proton conduction was observed at ∼5 nm thick film but was still much higher than for carbon substrates. These results indicate that the number of active proton-conductive pathways and/or the connectivity of the proton path network changed with film thickness. The surface morphology of thinner films was significantly affected by the film/substrate interface and was fundamentally different from that of the bulk thick membrane.
ISSN:1463-9076
1463-9084
DOI:10.1039/c3cp51136g