Atomic-Scale Picture of the Electric Double Layer around a Heterogeneous Solid-Liquid Interface Based on 3D-RISM-SCF Theory

The structure of electric double layers (EDLs) has been one of the central subjects in electrochemistry. Atomic-scale insights are becoming increasingly necessary to understand the interface between a heterogeneous material and a dilute electrolyte solution. However, only solid-liquid interfaces with planar structures have mainly been investigated in theoretical studies due to the complexity of the interfaces. Therefore, we propose a theoretical approach based on 3D-RISM-SCF (three-dimensional reference interaction site model self-consistent field) to elucidate the properties of EDLs at the atomic scale. In this approach, density functional theory calculations are performed with a computational program applicable to nanostructures. The solvation structure around a charged material is obtained using a statistical mechanical theory for molecular liquids, the 3D-RISM theory, which provides density distribution functions of a dilute solution around a heterogeneous material at a reasonable computational cost. Furthermore, the contribution of a finite charge to the solvation structure is evaluated using a semianalytical framework to deal with EDLs. The proposed approach is applied to an EDL between a graphite-supported Pt-13 heterostructure and a KCl aqueous solution. The analysis of the atomic charge, solvation structure, and electrostatic potential profile reveals that the EDL structure significantly depends on the atomic-scale details of the heterostructure.