Abstract
Reported herein is a neutron reflectometry (NR) study on hydrated Nafion thin films (∼30 nm) on a silicon substrate with native oxide. The Nafion morphology is investigated systematically across the whole relative humidity range using both H2O and D2O vapours to enable a comparative study. By utilising this systematic approach two key results have been obtained. The first is that by leveraging the strong positive scattering signal from the D2O vapour, a complete and systematic water adsorption isotherm (Type II) for a Nafion thin film is produced. Utilising the slight negative scattering signal of the H2O enabled the quantification of the hydration dependent evolution of the formation of Nafion/water lamellae near the substrate surface. The number of lamellae layers increases continuously with hydration, and does not form abruptly. We also report the effects of swelling on the thin films across the relative humidity ranges. The work reported should prove useful in quantifying other hydration dependent properties of Nafion thin films such as conductivity and understanding Nafion/semiconductor based devices, as well as showcasing a NR methodology for other hydrophilic polymers.
| Original language | English |
|---|---|
| Pages (from-to) | 28554-28563 |
| Number of pages | 10 |
| Journal | Physical Chemistry Chemical Physics |
| Volume | 24 |
| Issue number | 46 |
| DOIs | |
| State | Published - Nov 22 2022 |
Funding
This work was funded by the Australian Research Council (ARC) under DP170104024 and DP170102552, the Welsh European Funding Office (European Regional Development Fund) through the Sêr Cymru II Program. P. M. is a Sêr Cymru II National Research Chair, which is supported by the Welsh Government through the European Regional Development Fund and an Honorary Professor at the University of Queensland. A. B. M. is a Sêr Cymru II fellow and the results incorporated in this work is supported by the Welsh Government through the European Union's Horizon 2020 research and innovation program under the Marie Skłodowska-Curie grant agreement No 663830. P. H. is funded by the Welsh Government's Sêr Cymru II Program through the European Regional Development Fund, Welsh European Funding Office, and Swansea University Strategic Initiative in Sustainable Advanced Materials. This work was performed in part using the NSW node of the Australian National Fabrication Facility (ANFF).