Characterization and Modeling of Free Volume and Ionic Conduction in Multiblock Copolymer Proton Exchange Membranes Articles uri icon

publication date

  • May 2022

start page

  • 1688

end page

  • 1708

issue

  • 9

volume

  • 14

International Standard Serial Number (ISSN)

  • 2073-4360

abstract

  • Free volume plays a key role on transport in proton exchange membranes (PEMs), including
    ionic conduction, species permeation, and diffusion. Positron annihilation lifetime spectroscopy and
    electrochemical impedance spectroscopy are used to characterize the pore size distribution and ionic
    conductivity of synthesized PEMs from polysulfone/polyphenylsulfone multiblock copolymers with
    different degrees of sulfonation (SPES). The experimental data are combined with a bundle-of-tubes
    model at the cluster-network scale to examine water uptake and proton conduction. The results show
    that the free pore size changes little with temperature in agreement with the good thermo-mechanical
    properties of SPES. However, the free volume is significantly lower than that of Nafion®, leading to
    lower ionic conductivity. This is explained by the reduction of the bulk space available for proton
    transfer where the activation free energy is lower, as well as an increase in the tortuosity of the
    ionic network.

keywords

  • pals; electrochemical impedance spectroscopy; modeling; ionic conductivity; free volume; spes; proton exchange membrane