What is it about?
In order to monitoring the groups -OH of the Nafion®, we used the Photoacoustic Spectroscopy phases. The optical absorption spectrum was determined for wavelengths of 800 to 2600 nm. The procedure was to measure the samples in different hydration times. Using the Phase-Resolved Photoacoustic method, it was possible to separate the contribution of –OH, of C=O and of methylene group. The phase lag as a water function behaviors found may be associated with structural changes induced by membrane hydration.
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Why is it important?
Nafion® membranes were developed by DuPont, a perfluorosulfonic acid/polytetrafluoroethylene copolymer. These membranes are hydrophilic and the water is preferentially sorbed into the clusters due to the hydrophobic character of fluorocarbon matrix. The sulfonic acid groups are chemically active and fixed within the Teflon polymer matrix. Thus, this first synthetic ionic polymer is chemically resistant and durable, making it useful for Proton Exchange Membrane fuel cells.
Perspectives
Photoacoustic spectroscopy allowed a non-destructive investigative analysis of the material, and monitoring their hydration. The membrane spectroscopic study indicated the different behaviors of the OH absorption bands that enabled the monitoring of hydration in Nafion®. The results showed a sudden increase of the PA signal in the early hours of hydration and possible saturation. The PRPA was able to separate the bands OH combinations of terminal methylene groups and C=O stretches. The behavior of the phase difference as a hydration time function predicts the results for the thermal diffusivity and the constant structural change, primarily related to the change in the number of ion clusters. In general, the findings showed that for best performance of the Nafion® membrane is optimum for the higher thermal diffusivity region and anterior to saturation (1 h).
Professor Daniele T Dias
Federal University of Technology - Paraná
Read the Original
This page is a summary of: Spectroscopic study of Nafion® membrane as a function of water content by Phase-Resolved Photoacoustic Method, Revista Brasileira de Física Tecnológica Aplicada, May 2016, Universidade Tecnologica Federal do Parana (UTFPR),
DOI: 10.3895/rbfta.v3n1.3768.
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