The nanophase-segregated structure and transport properties of quaternary ammonium grafted polycation membranes are investigated in order to characterize the effect of molecular structures of quaternary ammonium using a molecular modeling method. We build model structures using density functional theory calculations with B3LYP and 6-31G**, providing optimized geometries and Mulliken charges. Then force field based models are simulated in the presence of water molecules using molecular dynamics simulation method. After equilibrating molecular arrangement and packing in a simulation box, we perform long-run MD simulations to evaluate the local and global distribution of water and hydroxide molecules. The extent of nanophase-segregation is evaluated by the structure factor analysis, which can be compared with the experimental small angle scattering data. The molecular transport of water and hydroxide is also analyzed via monitoring the molecular mean-square displacement by assuming Gaussian diffusion. The results of the anion exchange membrane fuel cell are compared to those of the proton exchange membrane fuel cell.

Molecular dynamics simulation of quaternary ammonium polycation exchange membrane fuel cell: Nanophase-segregated structure and transport properties

256th National Meeting (2018)

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