(605b) Investigating the Molecular Nature of Electrostatic Screening in the Double Layer

The electrochemical double layer (EDL) is a ubiquitous feature of solid-electrolyte interfaces, and plays an important role in screening the bulk electrolyte from strong electric fields imposed at the interface. Several theories have been developed to describe the spatial profile of the electrostatic potential in the EDL; the most prominent one is Gouy-Chapman theory, which predicts an exponential decay of the electrostatic potential over the concentration-dependent Debye screening lengthscale. We evaluate the merits of the Gouy-Chapman picture by drawing comparisons to results from atomistic simulations of electrochemical interfaces held at constant potential. While some features of exponential screening are recovered, our results show salient excursions from Gouy-Chapman theory, and underscore the important role of orientable solvent molecules in screening electric fields at the interface.