(215a) Structure and Charging Kinetics of Electrical Double Layers at Large Electrode Voltages

The structure and charging kinetics of the electrical double layers (EDLs) near polarized electrodes play a key role in many nano-devices such as AC electroosmosis-based nanofluidic pumps. It is thought that the EDLs near electrodes with low voltages and in dilute electrolytes can be described by the classical theories such as the Poisson-Nernst-Planck equations. However, the EDLs near electrodes with large voltages and in concentrated electrolytes are much less understood. Several important works on these problems have been recently reported, e.g., it has been postulated that, at large electrode voltages, the counter-ion concentration near the electrodes may approach the steric limit and modified PNP equations capable of accounting for such effects have been proposed. These works mostly adopt continuum theory approaches and thus have significant advantages in term of generality. However, owing to the complex nature of the EDL, it is challenging to include all aspects of the EDL in such approaches.

In this presentation, we report molecular dynamics (MD) simulation of the EDLs at the interfaces of concentrated NaCl solution and planar electrodes under large voltages. The MD simulation results on the equilibrium structure and charging kinetics of the EDL will be compared against the predictions by the classical Poisson-Nernst-Planck model and the linear RC model.