Towards constant potential modeling of CO-CO coupling at liquid water-Cu(1 0 0) interfaces

Abstract We use density functional theory, molecular dynamics, and metadynamics to study electrochemical *CO–*CO coupling in explicit electrolyte. We consider both the *CO–*CO coupling reaction and the charging process required to keep the potential constant. The charging process consists of transferring explicit cations from the electrolyte and electrons from the potentiostat to the interface. Under constant charge conditions (non-constant electrostatic potential), the *CO–*CO coupling reaction energies are relative insensitive to the charge state at the interface and the electrolyte composition and the reaction occurs with co-adsorption of water. Under constant potential conditions, the *CO–*CO coupling reaction is stabilized at lower potentials because of charging, the reaction is influenced by the electrolyte composition, and water-coadsorption is reduced. The *CO–*CO coupling reaction changes the electrosorption valency by around 0.4–0.5. We propose a simple approach to convert energetics from constant charge to estimates at constant potential. The approach is generally applicable to electrochemical processes.