Electrocatalytic reactions occur within the electric double layer (EDL) [1], where the applied potential, interfacial charge distribution, and electrolyte structure jointly determine reaction energetics and kinetics [2]. Key interfacial descriptors such as the potential of zero charge (PZC), the double‐layer capacitance (C_dl), and the solvation state of ions govern how electric fields, charge transfer, and molecular orientation evolve at electrified interfaces, yet their microscopic origins remain insufficiently understood [3,4]. Establishing robust links between these interfacial properties and atomic‐scale structure is essential for the rational interpretation and design of electrocatalysts for emerging bond‐forming and bond‐breaking transformations.

This poster synthesizes complementary theoretical and experimental insights to establish a molecular‐level framework for electrochemical interfaces at metal–water boundaries. A key focus is the large scatter in PZCs reported from ab initio molecular dynamics (AIMD) simulations for benchmark electrocatalysts such as Pt and Au, which is shown to arise from the choice of reference potential schemes and computational setup. To address this issue, a revised work‐function–based approach (revWF) is introduced, enabling a more robust and transferable determination of PZC directly from AIMD simulations. Building on this consistent electrostatic referencing, the consequences of interfacial polarization are examined through the double‐layer capacitance of platinum surfaces, revealing that the experimentally observed decrease of C_dl from the double‐layer to the hydrogen underpotential deposition regime originates from a transition between compensating and non‐compensating charge‐transfer and orientational polarization contributions, rather than from hydrogen adsorption itself. Finally, the role of the applied potential in shaping ion solvation is explored by constructing solvation‐state diagrams from AIMD‐derived free‐energy barriers within an electrostatic framework, which predict the preferred solvation and spatial distribution of alkali cations near electrode surfaces.

Together, these results clarify how electrostatic referencing, interfacial polarization, and ion solvation jointly govern electrochemical interfaces, providing transferable concepts relevant to catalyst design and mechanistic understanding in emerging electrocatalytic transformations.