(465f) Modeling Constant-Potential Dynamics and Free Energetics of Electrochemical Interfaces

Electrochemistry takes place at the electrode/electrolyte interface under applied potential. The orientation and organization of solvent molecules greatly influence the reaction energetics, and all these are dependent on the electrode potential. These complexities are not accounted for in implicit solvation models and constant-charge DFT calculations.

In this work, we present EChO (ElectroCHemical Optimizer), a python interface, which enables local optimization, MD, and constrained MD simulations at grand canonical DFT (GC-DFT) level to gain insights into fixed-potential configurations, interfacial dynamics, and free energetics of electrochemical reactions. We will cover the implementation of the code, and its application to understand the pH dependence of alkaline HER on Pt, and the role of Rh dopant on Pt in alkaline HOR. The insights into the orientation of surface water layers, the role of surface adsorbates on local solvation structure, partial surface charging, and their implication on reaction energetics can only be gained through the constant-potential treatment.