Polarization Effects in Dynamic Interfaces of Platinum Electrodes and Ionic Liquid Phases: A Molecular Dynamics Study

M Buraschi and S Sansotta and D Zahn, JOURNAL OF PHYSICAL CHEMISTRY C, 124, 2002-2007 (2020).

DOI: 10.1021/acs.jpcc.9b10354

We outline molecular dynamics simulations of electrode-ionic liquid interfaces with explicit consideration of electronic polarization effects. For this, conventional molecular mechanics are extended by the charge equilibrium approach, leading to moderate computational demand that still allows 10 ns scale dynamics studies of 10 nm scale models of atomic detail. The importance of local charge fluctuations is illustrated by comparing our models with the simplified picture of identical atom charges at the electrode surfaces. Already at idealized flat (110) and (111) platinum surfaces, we find that the migration of anions and cations induces local charge fluctuations on the electrode within a range of -0.2 to +0.2e, respectively. Heterogeneous charge distribution becomes even more critical when investigating rough surfaces. By the example of (1-butyl-3-methylimidazolium), acetate, and hexafluorophosphate, we show selective ion association from the ionic liquid phase to the surface steps of platinum electrodes as a function of the applied voltage.

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