Vanadium Ion Dynamics of Ionomer-Nanoparticle Hybrid Membranes*

Herein, the dynamics of water and hydrated vanadium ions in Nafion–NP membranes was investigated via quasi-elastic neutron scattering (QENS), specially, high-flux backscattering. The broadening of the energy spectra was attributed to the incoherent scattering from hydrogen atoms – both protons and water molecules in the vanadyl ion hydration sphere. These quasi-elastic events were deconvoluted from the scattering data through peak fitting in Data Analysis and Visualization Environment. Vanadium ion dynamics were measured for Nafion–NP membranes prepared through both a sol-gel condensation and solution casting process. The silica nanoparticle (SiNP) loading in these membranes was varied from 0 mass% to 10 mass%. The q-dependent peak shape parameters and elastic incoherent structure factors were extracted from analysis of the data using a jump diffusion within a sphere model. A delta function and a lorentzian function were applied in the fitting to extract information for both jump diffusion and local motion. By comparing the ion dynamics from these two types of ionomer nanocomposite membranes, the impact of SiNPs on the ion transport in these nanocomposites was better explained, providing deeper insight into the decreased vanadium ion crossover observed for these membranes.