A charge calibration strategy for describing the charge transfer during the electrochemical elementary step

Constant potential modeling of electrocatalytic processes remains a significant challenge in the field of computational catalysis, primarily due to the difficulty in simultaneously considering the influence of constant potential conditions, explicit solvent environment, and the double-layer structure. In this work, we propose a charge calibration strategy for electrocatalytic processes. This strategy accounts for charge transfer in systems with explicit solvation and ions during constant-potential free energy modeling. In our strategy, interfacial counter-ions are employed to model the Helmholtz layer and determine the surface charge density, which defines the electrode potential. During the simulation of electrochemical reactions, extra charges are introduced/extracted to/from the system to compensate for electron transfer between the electrode and the reaction species and keep a constant surface charge density along the reaction profile. Our method showcases the impact of potential-dependent solvent reorganization on reaction kinetics and underscores the importance of constant potential kinetics. We anticipate that the strategy presented here will inspire further theoretical and experimental studies for electrochemistry interfaces.