Ph.D. candidate, Apoorv Balwani, successfully defends his dissertation

April 28, 2020

Congratulations to Apoorv Balwani for successfully defending his dissertation titled “Impact of Nanoparticles on the Segmental Dynamics and Transport Properties of Ionomer Nanocomposite Membranes”.  Apoorv’s advisor is Dr. Eric Davis.

Nanocomposites of perfluorosulfonic acid ionomers and silica nanoparticles play a pivotal role in large scale, grid integratable Vanadium redox flow batteries. Impregnation of these ionomers with inorganic nanoparticles has gained prominent standing in recent years due to the ease and scalability of fabrication of ionomer nanocomposites and a desirably tuned vanadium ion selectivity, although the specific mechanisms underlying the slowdown of vanadium ion transport by these inorganic moieties presently elude us. In this work, Nafion-silica nanocomposites were characterized to investigate the correlation between their aqueous transport properties and their segmental dynamics as a function of heat treatment and nanoparticle concentration in order to elucidate the mechanism of vanadium ion crossover suppression as a function of structural dynamics, hydration state and nanoparticle sequestration and loading.

The water sorption kinetics of Nafion-SiNP nanocomposites were investigated with in situ time resolved attenuated total reflectance Fourier transform infrared spectroscopy (tATR-FTIR) while the impact of nanoparticles on structure dynamics of the nanocomposites were characterized with neutron spin echo spectroscopy (NSE) and broadband dielectric  spectroscopy (BDS). The hydration kinetics and viscoelastic swelling behavior were seen to be highly concomitant in the tATR-FTIR studies, while investigations with NSE and BDS correlate this change in viscoelastic behavior to the molecular scale nanoparticle-ionomer interactions.

Finally, quasielastic neutron scattering is employed to quantify the vanadium ion dynamics in fouled membranes with varying degrees of silica incorporation. The results from this study enlighten the mechanism of slowdown of ionomer segments due to electrostatic ionomer-nanoparticle interactions, and present an investigative framework which can be translated across different ionomer-nanocomposite systems to characterize water-mediated transport.