Charge Relaxation Dynamics of an Electrolytic Nanocapacitor

    Authors

    V. Thakore;J. J. Hickman

    Comments

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    Abbreviated Journal Title

    J. Phys. Chem. C

    Keywords

    LATTICE BOLTZMANN METHOD; NUMERICAL-SOLUTION; CIRCUIT MODELS; ELECTRIC-FIELD; EQUATION; SIMULATION; EQUILIBRIUM; FLOWS; INTERFACE; ADVECTION; Chemistry, Physical; Nanoscience & Nanotechnology; Materials Science, ; Multidisciplinary

    Abstract

    Understanding ion relaxation dynamics in overlapping electric double layers (EDLs) is critical for the development of efficient nanotechnology-based electrochemical energy storage, electrochemomechanical energy conversion, and bioelectrochemical sensing devices as well as the controlled synthesis of nanostructured materials. Here, a lattice Boltzmann (LB) method is employed to simulate an electrolytic nanocapacitor subjected to a step potential at t = 0 for various degrees of EDL overlap, solvent viscosities, ratios of cation-to-anion diffusivity, and electrode separations. The use of a novel continuously varying and Galilean-invariant molecular-speed-dependent relaxation time (MSDRT) with the LB equation recovers a correct microscopic description of the molecular-collision phenomena and enhances the stability of the LB algorithm. Results for large EDL overlaps indicated oscillatory behavior for the ionic current density, in contrast to monotonic relaxation to equilibrium for low EDL overlaps. Further, at low solvent viscosities and large EDL overlaps, anomalous plasmalike spatial oscillations of the electric field were observed that appeared to be purely an effect of nanoscale confinement. Employing MSDRT in our simulations enabled modeling of the fundamental physics of the transient charge relaxation dynamics in electrochemical systems operating away from equilibrium wherein Nernst-Einstein relation is known to be violated.

    Journal Title

    Journal of Physical Chemistry C

    Volume

    119

    Issue/Number

    4

    Publication Date

    1-1-2015

    Document Type

    Article

    Language

    English

    First Page

    2121

    Last Page

    2132

    WOS Identifier

    WOS:000348753000058

    ISSN

    1932-7447

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