Year: 2025
Type: article
Abstract: High Resolution Image Download MS PowerPoint Slide Inorganic fillers are commonly integrated into ion-exchange membranes to alter water hydration, improve ion conductivity, and tune transport properties. Here, we measure water uptake and diffusion in Nafion, which contains various concentrations of TiO 2 (0–5 wt %). With adsorption–desorption isotherms measured by dynamic vapor sorption, we probe the moisture kinetics and find a maximum change in hydrated Nafion mass by water vapor adsorption at 2 wt % TiO 2 . Pulsed field gradient nuclear magnetic resonance (NMR) reveals that with increasing TiO 2 concentration, the two measured components of water diffusion are also maximized at 2 wt % TiO 2 . The first component had a diffusion coefficient, on the order of 1 × 10 –9 m 2 /s, which approaches the diffusion of free water. Observing root-mean-square displacement as a function of increasing observation time indicates that this water population is affected by the ionomer-TiO 2 morphology. The second component had a diffusion coefficient on the order of 1× 10 –11 m 2 /s, which is attributed to water molecules that interact more strongly with sulfonic acid groups. With solid-state proton NMR relaxometry under low (near 0%) and high (near 100%) relative humidity, we measure T 1 and T 2 relaxation of water molecules on different time scales. Hydrated Nafion+2 wt % titania offers the highest water relaxation times with T 1 = 413 ms and T 2 = 4.77 ms. This high T 1 /T 2 ratio further indicates a two-component water environment and semirestricted water diffusion.
Institution: Georgia Institute of Technology
Language: English
Subfield: Electrical and Electronic Engineering
Field: Engineering
Domain: Physical Sciences
Open Access status: hybrid
Estimated APC paid: $4,500
OpenAlex ID: W4410520601