Role of Nanoparticle Size and Surface Chemistry on Ion Transport and Nanostructure of Perfluorosulfonic Acid Ionomer Nanocomposites

Published

March 7, 2022

Author(s)

Allison Domhoff, Tyler Martin, Eric Davis

Abstract

Perfluorosulfonic acid (PFSA) ionomer nanocomposites have emerged as a promising solution to the low ion selectivity of ionomer membranes utilized in flow batteries, such as vanadium redox flow batteries (VRFBs). Herein, we present a systematic investigation of the impact of silica nanoparticle (SiNP) size and surface chemistry on the nanoparticle dispersion state and the resulting morphology and vanadium ion permeability of the composite membranes. Specifically, Nafion containing a mass fraction of 5 % silica particles, ranging in nominal diameters from 10 nm to >1 m and with both sulfonic acid- and amine-functionalized surfaces, were fabricated. Most notably, an approximately 80 % reduction in vanadium ion permeability is observed for ionomer membranes containing amine-functionalized SiNPs at a nominal diameter of 200 nm. Trends in vanadium ion permeability with particle size were seen to be a function of the surface chemistry, where permeabilities were seen to increase and remain relatively constant with increasing particle size for membranes containing unfunctionalized and amine-functionalized membranes, respectively. In general, the silica particles tended to exhibit a higher extent of aggregation as the size of the particles was increased, though the sulfonic acid-functionalized particles were seen to be better dispersed, at all particle sizes, than either the unfunctionalized and the amine-functionalized particles. From small-angle neutron scattering (SANS) experiments, an increase in the spacing of the hydrophobic domains was observed for all composite memrbanes, though the impact of particle size and surface chemistry were seen to have varying impacts on the spacing of the ionic domains of the ionomer.

Citation

Soft Matter

Issue

17

Pub Type

Journals

Download Paper

https://doi.org/10.1039/D1SM01573G

Local Download

Keywords

nanocomposites, membranes, vanadium redox flow batteries, neutron scattering

Citation

Domhoff, A. , Martin, T. and Davis, E. (2022), Role of Nanoparticle Size and Surface Chemistry on Ion Transport and Nanostructure of Perfluorosulfonic Acid Ionomer Nanocomposites, Soft Matter, [online], https://doi.org/10.1039/D1SM01573G, https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=932166 (Accessed October 11, 2025)